Is your iPhone mirroring and other continuity features not working? Check if you have a bluetooth dongle attached.

I have been having this issue for months (since the betas started for MacOS 15 Sequoia) and have been searching and searching for a fix. Nothing. I have seen people online, in particular this subreddit, begging Apple for a fix. My Mac spent a whole week in the Apple Store this past week. No luck. It still persisted. Then today, I started unplugging shit and found something was doing it. It was a pluggable Bluetooth dual-mode dongle. I actually started using it at the beginning of the MacOS beta because the first dev beta caused Bluetooth to crash unexpectedly (prior to the release of iPhone Mirroring). **If you're having issues with Continuity, iPhone mirroring, PCI-E kernel panics, Ethernet crashes, etc., check your dongles.** That is what was doing it for me, and the Apple Store wasn't able to see it because I never took the dongles in and it didn't show specifics on the kernel panics. I have let Apple know so they can hopefully provide a fix, but don't count on it. Go ahead and see if this works for you.