via Mailman-users writes:
Thank you for the reply. Ultimately, I ended up digging deeper into the allauth docs, per your suggestion, and I went a little bit further with the "SOCIALACCOUNT_ONLY" option. It turns out that the errors I were seeing were related to the sign up button referencing a view that didn't exist.
You have to do this, I suspect (I am unsure that removing the reference from urls.py would protect you from A Sufficiently Smart Miscreant, and if it did you'd still get the error, so why not remmove the code and remove all doubt!)
I solved this in an admittedly ugly way, by removing the sign up button from the postorius and hyperkitty templates.
You do not have to do it this way. There is a search path for templates, and you can remove those buttons from copies stored in a directory earlier in the path. I use /etc/mailman3/templates/..., but they can go anywhere convenient that won't be overwritten by an upgrade. The worst that could happen is the copies get removed, and then you get the error, which you fix.