I’ve been self-hosting Matrix Synapse for more than two years to chat friends and family and it has been rock-solid and it’s on a VPS that os hosting a Nextcloud and Lemmy instance as well. It is definitely not really resource hungry for small groups of people.
If you want to try again this route, just make sure that everybody saves a backup of their keys as the messages are all encrypted and while you can authenticate a new client installation from another client that the same user is logged in, some people - like my mother - only use one, on her phone, which is understandable.
So in summary, I’m very happy with it! :)
That is a good point… on average it’s around 500Mb of RAM usage, between 0.5% and 1% of CPU (it’s a 2.4Mhz four cores).
Space is 5Gb, mainly media files accumulated over two years.
So overall, not bad.