Imagine that you use jj, while everyone else who works on the repo along with you uses regular git.

Is it easy?

Yes, that describes me at both jobs I’ve had since learning jj. Hence why I asked for specifics: I’m genuinely curious what other people struggle with, partially because I’d like to help them if I can, and partially because it gives me a better understanding of common pitfalls which helps when teaching other people.

Yes, that is the case for almost every repo I’ve ever used jj for. It is a complete non-issue. There is virtually zero friction.

I believe this is the most common scenario, yes. If you're used to actively pushing and pulling from the same branche as your colleagues, you need to learn how to manipulate diverging changes and conflicting bookmarks, but other than that all the jj magic is limited to your local activity.

I do this all the time at my job, without issue. I think it's honestly easier than using plain git.

yeah nobody "has to know", especially if everyone else is also rebasing etc constantly.

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.