ok, i have deleted the user, but actually deleting of the official waring had not helped.
i still got the same error message when i was trying to delete the user from admin panel, when just clicked on the user and pressed Delete User button in the bottom-right of the page.
what has worked out is the button Delete (yes, not Delete User) in the header of the page when going to Show Public Profile.
so it looks like those two delete buttons have different functionality. might be a bug?
New Discourse user here, playing with hosted instance since this morning, and now fiddling with authentication/authorization.
Hitting the exact same issue: a colleague of mine signed-up locally (note: I’ve also enabled a few oauth2 providers), then logged-out, then as admin I went to delete him (delete only) -> no can do (There was an error deleting that user. Make sure all posts are deleted before trying to delete the user.)
he has the discobot greetings PM in his inbox, deleting it did not make any difference
I got him to create a topic and then log back out, still can’t delete him
his email domain matches an auto-join primary group I defined (can’t remove him from the group either in fact, which I’m not sure is a feature or an anomaly given that his domain does match)
Let me know if any further info could help, I’ve tried to share as much relevant info from what I learned in just a day (started trial this morning).
Note: noticed other traces of such behaviour in this much more recent post
But that issue is closed, hence why I reached out here