Welcome to the deep rabbit hole :-) how much do you know about how computers work? In general, you’re going to need to understand some basic networking and general Linux administration, but if you already have a grasp on that then I’d say you just need to start small (simple service, aim to have a resilience goal with backups and restoration) and other metrics that motivates you. Perhaps you want to learn something new with every service you host? You decide, this is your hobby :-)

I think for matrix to be usable in a homelab setting, Matrix needs to enable a way to handle these huge data storage with prune or something similar.

I found snikket to be quite decent, give it a whirl.