Chungus

Can you share your firewall config? It could be that the firewall isn’t allowing packets to be forwarded from the tun/tap interface on the router to the LAN interface or vice versa.

Can you ping the ssh server from the phone?

I regret moving my phone number to Google Voice because at this point I fully expect Google to someday kill the service.

If they are on the same l2 network then your options are basically either to use nginx ACLs or a local firewall on the nginx host since the traffic wont traverse the firewall.

Something like iptables -I INPUT -s 1.2.3.0/24 -j DROP on the nginx host should work

I’ve been running a synapse server for a few years using https://github.com/spantaleev/matrix-docker-ansible-deploy

I’d highly recommend the above Ansible playbook as it makes it easy to manage not only synapse but also to manage a bunch of bridges and bots if you have the need for them. I have a bunch of rooms that are bridged to Slack for my bozo friends that refuse to use a cool open-source alternative.