How did you exactly install Express on the router? Did you use an app or something of that kind?
If the VPN provider has WireGuard support, you may wanna use a wireguard client software to connect to it. Flash OpenWRT on the router, install and configure a wireguard interface that connects to Express, then forward packets from behind LAN to that interface so they go through the VPN tunnel. A bit tricky for beginners, but I hope you can make it.
Since OpenVPN protocol seems to become unsupported in the future, Wireguard should be the way to go. Mullvad/IVPN should also support it, and once you know how to set it up it should be usable across many services and devices.
Do you recommend installing VPN apps on separate devices instead of the router?
For flexibility I’d do this. In case I’d wanna switch upstream servers for a single device without affecting others.
Non-federated Matrix server with rooms bridged to Discord/Whatsapp/Slack/whatever, so everyone can join.
Use standard webapps for other stuff like polls, surveys, events etc and send the URL to an announcement channel. Not sure of exact solutions but if one app can do it all and send email reminders for them, thatd be great. Same can be done for VoIP with Jitsi links, or even Z**m links.
Backup the databases if you need the chat logs. All of this should be doable with a small VPS, but a mini PCs cluster could be better