I've never tried jj, but recently I discovered lazygit which in my opinion comes pretty close to perfection.

Rebasing can be done instantly (reorder commits, fixups, squash), I can extract and reverse custom patches from previous commits, I can partially stage files, undo.

One think I like is that it explains what it does in terms of git commands. So it helps a little to have a good git mental model, and as such I guess it doesn't solve the same thing as jj.