@renbymon stock Mastodon. Though it it a bit heavy as a single user instance, would have preferred to go with something like GoToSocial instead (but it has its own..quirks...like needing a separate gui or client to use).
If you are going full Mastodon (or glitch-soc for that tasty markdown support), I suggest bumping the RAM up to about 8gb to give enough headroom for supporting services to run.
@renbymon saying that, usage isn't that bad just now, might get away with 4gb if you have fast swap