AFAIK there is no polished standalone frontend for jj yet. https://github.com/gulbanana/gg comes closest but I ran into some quirks when using it on git compatible/colocated repos.

Someone has made a VSCode plugin but it's closed source and I believe it will be paid at some point? https://www.visualjj.com/

If you are willing to use a TUI, jj-fzf (https://github.com/tim-janik/jj-fzf) has been wonderful and development is extremely active too.

I exclusively use git through the GUI, but the jj CLI improves so much over the git CLI that I'm willing to live with the CLI for now.

Still hoping that the GUIs become more polished though, and also for Inteliij IDEA integration.