Unstable systemd-resolved with multiple DNS servers

**Describe the bug**

I realized that my DNS was unstable from my machine for a while when I was connected to my home network where my router advertised multiple DNS servers. I found out that my current DNS server was constantly switching due to the systemd-resolved rules defined in OpenSnitch.

Include the following information:
- OpenSnitch version: `1.6.3-1`
- OS: `Arch Linux`
- Version: ` `
- Window Manager: `KDE`
- Kernel version: echo $(uname -a) `Linux personal 6.4.12-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 24 Aug 2023 00:38:14 +0000 x86_64 GNU/Linux`

**To Reproduce**

First, I enabled the debug logs of systemd-resolved,

```
[Service]
Environment=SYSTEMD_LOG_LEVEL=debug
```

ends up in the `override.conf` via `sudo systemctl edit systemd-resolved`.

I observed that the DNS resolver was timing out, then it was forever switching to the alternative in the circular buffer. After I saw the host `detectportal.firefox.com` in the logs, I realized that OpenSnitch causes it.

```
journalctl -u systemd-resolved -f

Sep 08 10:25:15 personal systemd-resolved[23197]: Firing regular transaction 54198 for scope dns on wlan0/* (validate=yes).
Sep 08 10:25:15 personal systemd-resolved[23197]: Using feature level UDP+EDNS0 for transaction 54198.
Sep 08 10:25:15 personal systemd-resolved[23197]: Using DNS server 192.168.1.12 for transaction 54198.
Sep 08 10:25:15 personal systemd-resolved[23197]: Announcing packet size 1472 in egress EDNS(0) packet.
Sep 08 10:25:15 personal systemd-resolved[23197]: Emitting UDP, link MTU is 1500, socket MTU is 0, minimal MTU is 40
Sep 08 10:25:15 personal systemd-resolved[23197]: Sending query packet with id 54198 of size 53.
Sep 08 10:25:15 personal systemd-resolved[23197]: Emitting UDP, link MTU is 1500, socket MTU is 0, minimal MTU is 40
Sep 08 10:25:15 personal systemd-resolved[23197]: Sending query packet with id 54198 of size 53.
Sep 08 10:25:15 personal systemd-resolved[23197]: Timeout reached on transaction 42439.
Sep 08 10:25:15 personal systemd-resolved[23197]: Retrying transaction 42439.
Sep 08 10:25:15 personal systemd-resolved[23197]: Regular transaction 42439 for on scope mdns on wlan0/INET6 now complete with from none (unsigned; non-confidential).
Sep 08 10:25:15 personal systemd-resolved[23197]: Record personal.local IN AAAA fe80::6f7b:6165:5812:1ee1 successfully probed.
Sep 08 10:25:15 personal systemd-resolved[23197]: Sending response packet with id 0 on interface 3/AF_INET6 of size 140.
Sep 08 10:25:15 personal systemd-resolved[23197]: Freeing transaction 42439.
Sep 08 10:25:15 personal systemd-resolved[23197]: Got message type=method_return sender=org.freedesktop.DBus destination=:1.1166 path=n/a interface=n/a member=n/a cookie=19 reply_cookie=23 signature=n/a error-name=n/a error-message=n/a
Sep 08 10:25:15 personal systemd-resolved[23197]: Match type='signal',sender='org.freedesktop.DBus',path='/org/freedesktop/DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0=':1.1167' successfully installed.
Sep 08 10:25:15 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1168 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1 interface=org.freedesktop.DBus.Properties member=GetAll cookie=2 reply_cookie=0 signature=s error-name=n/a e>
Sep 08 10:25:15 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1168 path=n/a interface=n/a member=n/a cookie=25 reply_cookie=2 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:15 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1168 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_32 interface=org.freedesktop.DBus.Properties member=GetAll cookie=3 reply_cookie=0 signature=s error-n>
Sep 08 10:25:15 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1168 path=n/a interface=n/a member=n/a cookie=26 reply_cookie=3 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:15 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1168 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_33 interface=org.freedesktop.DBus.Properties member=GetAll cookie=4 reply_cookie=0 signature=s error-n>
Sep 08 10:25:15 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1168 path=n/a interface=n/a member=n/a cookie=27 reply_cookie=4 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:15 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1168 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_34 interface=org.freedesktop.DBus.Properties member=GetAll cookie=5 reply_cookie=0 signature=s error-n>
Sep 08 10:25:15 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1168 path=n/a interface=n/a member=n/a cookie=28 reply_cookie=5 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:15 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1168 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_35 interface=org.freedesktop.DBus.Properties member=GetAll cookie=6 reply_cookie=0 signature=s error-n>
Sep 08 10:25:15 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1168 path=n/a interface=n/a member=n/a cookie=29 reply_cookie=6 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:16 personal systemd-resolved[23197]: Sending response packet with id 0 on interface 3/AF_INET of size 82.
Sep 08 10:25:16 personal systemd-resolved[23197]: Sending response packet with id 0 on interface 3/AF_INET6 of size 140.
Sep 08 10:25:17 personal systemd-resolved[23197]: varlink: New incoming connection.
Sep 08 10:25:17 personal systemd-resolved[23197]: varlink-29: Setting state idle-server
Sep 08 10:25:17 personal systemd-resolved[23197]: varlink-29: New incoming message: {"method":"io.systemd.Resolve.Monitor.SubscribeQueryResults","parameters":{},"more":true}
Sep 08 10:25:17 personal systemd-resolved[23197]: varlink-29: Changing state idle-server → processing-method-more
Sep 08 10:25:17 personal systemd-resolved[23197]: varlink-29: Sending message: {"parameters":{"ready":true},"continues":true}
Sep 08 10:25:17 personal systemd-resolved[23197]: 1 clients now attached for varlink notifications
Sep 08 10:25:17 personal systemd-resolved[23197]: varlink-29: Changing state processing-method-more → pending-method-more
Sep 08 10:25:17 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1169 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1 interface=org.freedesktop.DBus.Properties member=GetAll cookie=2 reply_cookie=0 signature=s error-name=n/a e>
Sep 08 10:25:17 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1169 path=n/a interface=n/a member=n/a cookie=30 reply_cookie=2 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:17 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1169 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_32 interface=org.freedesktop.DBus.Properties member=GetAll cookie=3 reply_cookie=0 signature=s error-n>
Sep 08 10:25:17 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1169 path=n/a interface=n/a member=n/a cookie=31 reply_cookie=3 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:17 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1169 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_33 interface=org.freedesktop.DBus.Properties member=GetAll cookie=4 reply_cookie=0 signature=s error-n>
Sep 08 10:25:17 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1169 path=n/a interface=n/a member=n/a cookie=32 reply_cookie=4 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:17 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1169 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_34 interface=org.freedesktop.DBus.Properties member=GetAll cookie=5 reply_cookie=0 signature=s error-n>
Sep 08 10:25:17 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1169 path=n/a interface=n/a member=n/a cookie=33 reply_cookie=5 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:17 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1169 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_35 interface=org.freedesktop.DBus.Properties member=GetAll cookie=6 reply_cookie=0 signature=s error-n>
Sep 08 10:25:17 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1169 path=n/a interface=n/a member=n/a cookie=34 reply_cookie=6 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:19 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1171 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1 interface=org.freedesktop.DBus.Properties member=GetAll cookie=2 reply_cookie=0 signature=s error-name=n/a e>
Sep 08 10:25:19 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1171 path=n/a interface=n/a member=n/a cookie=35 reply_cookie=2 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:19 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1171 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_32 interface=org.freedesktop.DBus.Properties member=GetAll cookie=3 reply_cookie=0 signature=s error-n>
Sep 08 10:25:19 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1171 path=n/a interface=n/a member=n/a cookie=36 reply_cookie=3 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:19 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1171 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_33 interface=org.freedesktop.DBus.Properties member=GetAll cookie=4 reply_cookie=0 signature=s error-n>
Sep 08 10:25:19 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1171 path=n/a interface=n/a member=n/a cookie=37 reply_cookie=4 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:19 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1171 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_34 interface=org.freedesktop.DBus.Properties member=GetAll cookie=5 reply_cookie=0 signature=s error-n>
Sep 08 10:25:19 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1171 path=n/a interface=n/a member=n/a cookie=38 reply_cookie=5 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:19 personal systemd-resolved[23197]: Got message type=method_call sender=:1.1171 destination=org.freedesktop.resolve1 path=/org/freedesktop/resolve1/link/_35 interface=org.freedesktop.DBus.Properties member=GetAll cookie=6 reply_cookie=0 signature=s error-n>
Sep 08 10:25:19 personal systemd-resolved[23197]: Sent message type=method_return sender=n/a destination=:1.1171 path=n/a interface=n/a member=n/a cookie=39 reply_cookie=6 signature=a{sv} error-name=n/a error-message=n/a
Sep 08 10:25:20 personal systemd-resolved[23197]: Timeout reached on transaction 54198.
Sep 08 10:25:20 personal systemd-resolved[23197]: Retrying transaction 54198, after switching servers.
Sep 08 10:25:20 personal systemd-resolved[23197]: wlan0: Switching to DNS server 1.1.1.1.
```

**Screenshots**

**Additional context**

Solutions I've found to remediate:

- Disable OpenSnitch (duh!!!)

- Disable any rules touching systemd-resolved (duh!!)

- In the systemd-resolved, hard-code the current the DNS server (duh!)

I'm not sure if this can be considered a bug in the end, because that's how systemd-resolved works(?); however, it caused some trouble to me so I'd be happy if there's a better way to fix it.