No subnetting in UTM

**Describe the issue**
I'm trying to build a cybersecurity Home Lab in UTM.
I'd like to simulate something moderately close to a real-world scenario, as other hypervisors do. I've been trying to configure each of my Ubuntu VM instances in different subnets. So far, the only connectivity I've had between them, is if they are on the same subnet.

I've spent lots of time trying to figure out how to set up an Ubuntu VM as a router to give connectivity to other Ubuntu VMs on UTM's Emulated VLAN, from different subnets. What I've tried so far doesn't seem to be working, which includes manually configuring the Advanced Network settings in each Ubuntu instance's Emulated VLAN network interface in UTM's settings. I've also configured the router's persistent iptable, as well as all of my instance's Netplan files to route through the Router VM.

I'm beginning to think that UTM doesn't support this for MacOS... the documentation gives very little insight or information.

Any help would be appreciated.
Thank you! :)

**Configuration**
* UTM Version:
* macOS Version: Ventura 13.3
* Mac Chip (Intel, M1, ...): M1