Recently I've had two issues:
- Mojave Universal Clipboard stopped working between Mojave and iOS 15.4.1
- Mojave notes iCloud synced but always showed a spinning activity icon
I found that I could make Universal Clipboard work again by creating or editing a note on my iPhone or on Mojave. Once that synced then UC worked until I rebooted.
I may have had success by:
- Changing my Mojave location DNS settings from Cloudflare (22.214.171.124) to Google (126.96.36.199). (Based on this post)
- Toggling Notes iCloud off then on again (restores notes)
Now the spinning is gone, and UC seems to be working.
Update 5/15/2022: UC is back to not working unless I create a note that's synced between iOS and Mojave. Notes doesn't show the skinny activity icon. So this is an open problem.