even weirder if it’s a Mastodon fork such as Glitch-soc, Hometown, Fedibird,… since they use older Mastodon versions as base
i myself have been active on calckey/firefish, hajkey and iceshrimp instances, and never had a problem interacting with people on mastodon forks > there had been some backfilling issues, but they got solved > but federation problems do exist: so far, it is not possible for *key users to interact with lemmy instances; also link posts from kbin do not show up on *key timelines