Found an active thread that seems to be actively following this issue. Doesn't look like reverting to Xcode 12.4 is a good idea also.
I have VS 2019 Community setup on my Windows (Version 16.9.4) and Mac (8.9.8 Build 7). Both respond that there are no updates available. When I "Pair to Mac" from the windows PC to the MAC it responds.
The Xamarin.iOS SDK version '126.96.36.199' that is installed on the Mac is not compatible with this version of Visual Studio. Would you like us to install Xamarin.iOS '188.8.131.52' for you? This will overwrite any other existing Xamarin.iOS installation on your Mac.
There were problems installing Xamarin.iOS from: 'https://aka.ms/xvs/pkg/macios/184.108.40.206'. Please try again and if the problem persists, try installing directly on the Mac and connect again.
I have reverted to doing work on the MAC as I am targeting IOS. I would like to use the Win PC as I am way more comfortable, but it's wonky when I try to build and deploy IOS. Most of the similar responses to version mismatch questions suggest ensuring that both versions are the same and up-to-date, which it seems they are. Looking that the versions referenced, I don't even see a version 220.127.116.11.
Any help would be great.
There seems to be a new update available of Visual Studio for Windows i.e. 16.9.5 which has support for XCode 12.5. Refer link for more details https://learn.microsoft.com/en-us/visualstudio/releases/2019/release-notes#16.9.5
So, I believe the update of VS for Windows to 16.9.5 should take care of your issue.
Mehul Harji Bhadricha