What happens if you put the unmodified "user_adapter.py" in place and add the ACCOUNT_ADAPTER string to the "settings.py" file.
I.e. I'm trying to determine if the issue is related to the modifications or if it occurs even with the unmodified "user_adapter.py" with the ACCOUNT_ADAPTER string added to the "settings.py" file.
It fails for both domains on the server with the ACCOUNT_ADAPTER string in "settings.py" and the unmodified "user_adapter.py".
This says to me that the "settings.py" is calling the "user_adapter.py" which, for some strange reason, is still trying to match a site(host) name.
And that suggests the modified "user_adapter.py" is still in there. So, I checked again that it was gone (yes it is gone) and rebooted the server.
No joy.
=====ERRORS====================
Webpage: 502 Bad Gateway
# tail -f /opt/mailman/web/logs/mailmanweb.log ... File "/opt/mailman/venv/lib/python3.11/site-packages/django/db/models/query.py", line 637, in get raise self.model.DoesNotExist( django.contrib.sites.models.Site.DoesNotExist: Site matching query does not exist.