Sorry, but I haven’t found a solution yet. It still doesn’t work on Sequoia 15.5. :/

I finally got it to work by closing Xcode and deleting everything in ~/Library/Developer/Xcode/UserData/Provisioning Profiles. It now even works without the REGISTER_APP_GROUPS build setting and supports automatic signing. By the way, I use automatic signing for all my projects, so it should be fine to delete all my provisioning profiles and let Xcode regenerate them, right?

Yes, I submitted FB14567843 but haven’t heard back from Apple. It’s still open, and there are no recent similar reports.

No, I haven’t found any workaround or guidance from Apple, so I’ve decided to hold off on shipping this feature for now.