Last night I updated Discourse and I was 100+ commits behind. After that all avatars (multisite) were gone. Registering new accounts would also have no avatar.
Did I miss a new setting or requirement? I know about the changes in the avatar system, but that worked fine. Something in the last 100+ commits changed this. Even the automatically generated avatars don’t work anymore.
And no, nothing in the logs.
BTW, I use Amazon S3, but all avatars now point to http://domain.ext/user_avatar/domain.ext/username/64/125.png, etc.