Just upgraded from bullseye to bookworm and getting the same errors. I fixed the "primary key type" warning by inserting this option:
DEFAULT_AUTO_FIELD='django.db.models.AutoField' at the bottom of /usr/share/mailman3-web/settings.py Now I'm stuck with the "timeout larger than retry": being a python/django noob I can't figure where to find the settings file where to edit those values...