I have now upgraded the Divisions by zero to Lemmy 0.19.0. I haven't seen any issues, but of course you will have to re-login.
Please check the new features here
I have also updated Pythörhead to be able to handle the new authentication (as well as the old), so if you're running a bot, make sure to update your Pythörhead dependencies.
Now is also a good time that you can support the running of this server. If you just want to support this instance, please use Ko-fi and you can get a custom emoji here. If you want to support my general development efforts as well (Lemmy, Pythorhead, Fediseer, Tagginator etc) feel free to use my liberapay
Is there a reason some instances wouldn't be federating correctly and others would?
I don't know. But there's already an issue about it: https://github.com/LemmyNet/lemmy/issues/4288
Also, the federation used to work on SDF after each upgrade for like 3 days, so it may or may not break later.