Day 2 trying to set up a mastodon/Fediverse instance... Have followed three different How-Tos, tried mastodon and two different alternatives... set up an empty server twice. I've never had so much trouble setting up a server software before! But, I'll persevere with this, as it's worth it!
Day 3.5 (well, it's 2am)
Finally!!
Umpteen attempts to install Mastodon, Pleroma, Misskey, Calkkey and another I've forgotten the bands of. Reinstalled two versions of Ubuntu three times before I copied the VM so could reset from that.
In the end, with the release of mastodon 4, I went back to that. Clean install of Ubuntu 20.04, followed the step by step. Found it told me to set up Ruby 3.0.3 when it then required 3.0.4, but otherwise it actually only bloody worked!