@NetscapeNavigator I don't know about Misskey's possible incompatibility, but as far as Mastodon is concerned, with this poll, it has nothing to do with a protocol change, it's supported in Mastodon's backend, and it was supported in Mastodon's front-end until 4.4.0 where it was accidentally broken
it is still possible to vote using a third-party client
and I have identified the issue and submitted a fix for the Mastodon front-end: https://github.com/mastodon/mastodon/pull/39949