Use whatever you have and test different setups. I would start by installing Proxmox and setup ZFS on some drive that not the boot partition. For just checking it out with some lightweight VMs and containers any CPU that’s not 20 years old will suffice, the more RAM the better. Play with VMs, backups etc in small scale. You can use your old external USB HDD, etc, just to figure out things like ZFS.
Don’t buy anything before getting some experience and having some kind of plan.
Hm, I never really liked Conversations and decided to end xmpp for good. Maybe I need to give it another try but I really like some Matrix features.
Better mobile clients? Have things changed this much in the least three years?
Last time I used Friendica I really disliked the UI but it keeps popping up lately, maybe there have been some improvements
Why not? It needs some moderation but it’s better than any general disquss-like solution imho.
You need different Subdomains as you suggested in your first paragraph. And add a reverse proxy like nginx or caddy to the machine which then proxies the different subdomains to the respective services (e.g. lemmy.your.site to localhost:2222, mbin.your.site to localhost:3333).
Theoretically, you could put a landing page behind some SSO/iam like authentik, and then link to the subdomains from the landing page, but eventually users will need be on the subdomain to use a specific site.
In Mastodon you need to mention the person you reply to or they won’t get mentioned. Clients usually set them automatically.