I'm looking at the code of the Apache authentication provider and it seems like it would not work properly. I don't use it or have a use case for it so I can't confirm.

It appears the call to function user_row_apache on this line is invalid:
https://github.com/phpbb/phpbb/blob/develop-ascraeus/phpBB/phpbb/auth/provider/apache.php#L140

Should that be $this->user_row() instead?