I accidentally found out that if you select your own phone from the Xcode’s list of devices where to run an app compilation, and then you select “Manage Devices...” for some reason, another Device Hub tab opens with your phone, and you can use it normally via macOS. It’s not exactly the "screen mirroring" feature, but it’s basically the same.

Here's a short video of the workaround: https://streamable.com/4fku9m