Screensaver password greyed out

1 - iPhone Mirroring system requirements

iPhone Mirroring can be used with only one Mac and one iPhone at a time. Your devices must meet these requirements.

• Your computer is a Mac with Apple silicon or Mac with the Apple T2 Security Chip and is using macOS Sequoia 15 or later.
• Your iPhone is using iOS 18 or later.

2 - You and I can not Remove the iPhone Mirroring Application for MacOS Sequoia

The application is Part of the Operating System which resides in a Sealed and Read Only Volume that cannot be opened by the User >> Full Stop

3 - Check and see of Profiles have been installed and used on this computer

With the iPhone Mirroring Not Supported message you see when launching iPhone Mirroring, are you still able to go to the iPhone Mirroring menu bar and choose Settings? If you can, then change it to "Ask Every time". This will allow you to adjust the setting in Lock Screen that was greyed out previously.

You may want to contact Apple Support directly: Official Apple Support

In the meantime, instead of using a Screen Saver you could just turn off the display after a time in System Settings > Lock Screen. I think that should work.

Having used, briefly, the iPhone Mirroring from an iPhone 15 Pro iOS 18.01 to a Qualifying Apple Computer Sequoia 15.0.1 >> Without an Profiles Used or Installed

Can not say any of the 3 machines I Own and Operate has these issues

Current Setting in Lock Screen for reference

If you what to try >>

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

Safe Mode will also eliminate Third Party Software, extensions and drivers from loading. It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 

Does the issue present in this mode ?

Sometimes a Safe Boot followed by a Normal Boot will just put things right.

This issue (require pw screen greyed out in lock screen pane) has been reported (and seen by me as well) after using the iPhone Mirroring app. To resolve you need to open the mirroring app then select settings then check the box for "ask everytime" (not the auto authorization). Then open preferences, lock screen and set PW requirement to none. However, since you cannot open the mirroring app not sure why you have the issue and the set PW field is grayed out. You can try this:

power down your iPhone completetly

restart your Mac

restart your Phone

This may clear out the issue