On lemmy.today, I don't appear to be seeing posts created in the past two days as of this writing on either !NonCredibleDefense@sh.itjust.works or !Games@sh.itjust.works. I am subscribed to both communities. I have not done an search to determine whether other subscribed sh.itjust.works communities are affected, though I assume that to be the case.
They are visible from lemmy.world, so the posts are propagating to at least some other federated instances.
sh.itjust.works presently appears to be running Lemmy 0.19.5 (versus lemmy.today's 0.19.4 and lemmy.world's 0.19.3). However, I do not think that this is a version-related problem, at least not alone, as !Ukraine@sopuli.xyz is showing up fine on lemmy.today.
https://lemmy.today/instances lists sh.itjust.works as a federated instance as of this writing.
https://sh.itjust.works/instances lists lemmy.today as a federated instance as of this writing.
Lemmy.today has also been responding very slowly to me over the past hour or so, and was frequently showing connection timeouts and gateway error pages when trying to load pages. Other instances appear to be working normally. That may be entirely unrelated, but I thought that I'd mention it, as it's unusual and at least might be related.
This can be useful: https://grafana.lem.rocks/d/bdid38k9p0t1cf/federation-health-single-instance-overview?orgId=1&var-instance=sh.itjust.works&var-remote_instance=lemmy.today