I use jj all the time for pull requests, in fact I don't use regular git at all anymore, and it's perfectly easy. Not only can I easily keep all my pull requests properly synced to their base branches, but I can easily and very quickly address review comments, keeping the commit stack clean without having to manually squash or amend or anything of that sort. Honestly it's a lot easier and more efficient than git for me because of how much naturally follows rather than requiring explicit imperative fixups.