Please try to comment and post things now, and see if they federate again.
Hopefully you see your activity instantly federated. I have tried making comments both to instances running Lemmy 0.19.1 and 0.18.5 and they all federate like they should.
Hope you have the same experience! 🥳
Yeah we need the new 0.19.2 version of Lemmy to hopefully fix things. Good news is that I saw it being worked on yesterday on github, so it should come very soon now. :)