lol. Haven't tried Matrix, but I've tried setting up NextCloud before.
I wish projects would look at #syncthing for inspiration.
Now there is a project that is just brain-dead simple to implement.
Just run the commands to add their apt repo, apt-get install it, run it from a cron job, and the rest is managed from the web interface. Stupid simple, and it has its own great NAT-traversing relays to keep all of your devices connected without having to use something like #tailscale.