Vdirsyncer does not work with iPhone hotspot on macOS

Everything works as expected on normal Wifi but fails when using a hotspot from a mobile phone.

I assume it times out, as there is a long pause between Sending request... and the error output.

vdirsyncer, version 0.19.3
Python version 3.12.7
macOS Sequoia 15.1

vdirsyncer -vdebug sync output:

debug: Fetching value for password.fetch with command strategy.
debug: Found cached value for ['command', ...].
Syncing calendar_posteo
debug: ====================
debug: PROPFIND 
debug: {'User-Agent': 'vdirsyncer/0.19.3', 'Content-Type': 'application/xml; charset=UTF-8', 'Depth': '1'}
debug: b'<?xml version="1.0" encoding="utf-8" ?>\n            <propfind xmlns="DAV:">\n                <prop>\n                    <resourcetype/>\n                    <getcontenttype/>\n                    <getetag/>\n                </prop>\n            </propfind>\n            '
debug: Sending request...
Syncing contacts_posteo
debug: ====================
debug: PROPFIND 
debug: {'User-Agent': 'vdirsyncer/0.19.3', 'Content-Type': 'application/xml; charset=UTF-8', 'Depth': '1'}
debug: b'<?xml version="1.0" encoding="utf-8" ?>\n            <propfind xmlns="DAV:">\n                <prop>\n                    <resourcetype/>\n                    <getcontenttype/>\n                    <getetag/>\n                </prop>\n            </propfind>\n            '
debug: Sending request...
error: Unknown error occurred for calendar_posteo: Cannot connect to host posteo.de:8443 ssl:default [None]
error: Use `-vdebug` to see the full traceback.
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/cli/tasks.py", line 74, in sync_collection
debug:     await sync.sync(
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/sync/__init__.py", line 149, in sync
debug:     a_nonempty = await a_info.prepare_new_status()
debug:                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/sync/__init__.py", line 55, in prepare_new_status
debug:     async for href, etag in self.storage.list():  # type: ignore[attr-defined]
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/storage/dav.py", line 853, in list
debug:     async for href, etag in super().list():
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/storage/dav.py", line 672, in list
debug:     response = await self.session.request(
debug:                ^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/storage/dav.py", line 413, in request
debug:     return await http.request(method, url, session=session, **more)
debug:            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/dfnrv7dckr3km3vi9lh3k1fpqdkprlx3-python3.12-vdirsyncer-0.19.3/lib/python3.12/site-packages/vdirsyncer/http.py", line 184, in request
debug:     response = await session.request(method, url, headers=headers, **kwargs)
debug:                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/xkaby9wz7izp9rgqf29f4fqcf0hlslv0-python3.12-aiohttp-3.10.8/lib/python3.12/site-packages/aiohttp/client.py", line 659, in _request
debug:     conn = await self._connector.connect(
debug:            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/xkaby9wz7izp9rgqf29f4fqcf0hlslv0-python3.12-aiohttp-3.10.8/lib/python3.12/site-packages/aiohttp/connector.py", line 557, in connect
debug:     proto = await self._create_connection(req, traces, timeout)
debug:             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/xkaby9wz7izp9rgqf29f4fqcf0hlslv0-python3.12-aiohttp-3.10.8/lib/python3.12/site-packages/aiohttp/connector.py", line 1002, in _create_connection
debug:     _, proto = await self._create_direct_connection(req, traces, timeout)
debug:                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
debug:   File "/nix/store/xkaby9wz7izp9rgqf29f4fqcf0hlslv0-python3.12-aiohttp-3.10.8/lib/python3.12/site-packages/aiohttp/connector.py", line 1293, in _create_direct_connection
debug:     raise ClientConnectorError(req.connection_key, exc) from exc

The traceback leads through vdirsyncer/storage/dav.py and vdirsyncer/http.py into aiohttp's connection setup. Reproduce the PROPFIND failure on macOS with normal Wi-Fi and an iPhone hotspot, then compare connection and timeout behavior. Done means identifying a reproducible cause and adding a focused fix or regression test for hotspot connections.