Some details arrived about the Android Developer Verification.

It won't use Play Protect, but will be a new service, for some inexplicit reason. There are some speculations in the article as to why it could be done this way, no way to say for sure at the moment, though.

Confirmed that ADB will be left alone, you will still be able to sideload through it.

Still no details if the thing can be turned off completely. If it won't be possible, I'm afraid that's still a death sentence for things like F-Droid.

There is hope that since it will be distributed as a separate package, maybe it will be possible to turn it off completely by disabling the verification package in ADB.

https://www.androidauthority.com/how-android-sideloading-restrictions-may-work-3595355/