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?

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### Update:
There is [this uncommented solution](https://discussions.apple.com/thread/251472179) 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.