iPhone Sync under Big Sur

I’m running MacOS 11.1 and iOS 14.3. I skipped Catalina and just updated to Big Sur.

Now that iPhone is managed through Finder rather than iTunes, when I plug my phone into USB I twice get a mandatory finder pop-up message that says “The file can’t be found.” Clicking OK in the pop-ups seems to have no effect. Clicking on the “?” mark in the pop-up message just gives me a blank help window.

Neither the Finder nor Photos opens/launches as has been my past experience. If I go to the Finder manually and open the iPhone device page. I find a sync session is stuck at Step 4 “Waiting for changes to be applied.”

If I try to abort abort the sync by clicking on the “x” in the device in the Finder’s sidebar nothing happens.

How can I sync my iPhone?