I remember being curious about the fediverse and when I first looked and saw "instances" I got decision fatigue.
I didn't know if an instance would limit me from interacting with others, could randomly disappear (ie hexbear domain), or if some instances would be a bad fit. I also didn't know of it was unchangeable. Decision fatigue set in and I was less excited, but still registered.
To overcome that, there should be a "randomly choose for me" button with notes next to it that say you can change later, it won't impact things, and you can interact with any instance. For random selection, just make it the top 3 most popular instances. Use a fun icon to indicate random change so the on boarding user has to think less.
Instances seem very confusing to an average user, as does federation. There could be an explanation like "Instead of 1 big company controlling everything, there are many copies of Lemmy that are in different places run by volunteers. These "instances" or copies are all Lemmy and can interact with each other, but having many copies means there isn't ever 1 big company who can set all the rules and suddenly change thing in a bad way. " and then the random selection button which almost everyone would choose.
The average user dosn't want to RTFM and also has an IQ of around 100 which is really low. The average reading ability of someone in the USA is like 6th grade level or something atrocious. You can't overestimate average intelligence in an in boarding process.