I upgraded to 2.4.0, and I'm stuck with the eternal admin password mess. Tried the fixlogin.php trick, didn't work. Is there any update for that one? Running PHP 8.0, the login page loads fine, the password doesn't work no matter what I do. Guess I should do more...

... should be listed in the server log. A second possible issue is the password hash. I think you were still on md5? We changed to sha and then ... archives works again, but the login is still broken (solvable with a fixlogin.php script).