I ended up having to make a Misago forum system live before I fully understand it all. Working rather well but two issues:
It's a vanilla Docker install.
1. Registration gives an 'unknown error' message but works. The message is putting people off.
2. Somewhat randomly people get the 'unknown error' message replying to threads - for some people it seems to happen all the time, for me randomly. Can't see mach logic to it.
I've found this thread 'misago-project.org/t/unknown-error-on-register-form/1091/' which describes the first problem, which relates to email service set-up. It's quite possible I've fouled this up. I need to go to my hosting provider to find out their email server details, but I don't know where I'g go in the Misago code to fix it. Is it possible that the post problem is related to the email too?
Edit: I find that I can't post a private thread - this suggests it is the same problem, connected to user name lookup
Edit2: I think I've got it. Email config is fouled up, leading to registration sending error message when it sends confirming email, or on password change, and on reply to post by user who has 'send email on reply' set.