When I connect my iPhone SE to my MacBook (Catalina 10.15.7) and open the Finder tab for the iPhone I am asked whether the Computer should trust this phone. When I click the button "Trust" I get the error:

Trust request error 0xE8000003

No connection is made.

This used to work nicely. I can connect this phone to other Macs. Also I can connect other phones to this Mac. Just these two don't want to get along in the Finder.

Btw, I can use the "Image Capture" app just fine!

How can I fix this?

Update:

There is this uncommented solution in the Apple forums, but running the first command:

sudo rm -rf /private/var/db/lockdown

already gives me a Operation not permitted even though the terminal has "full disk access" permissions.