Starting with Visual Studio 2019 version 16.7 Preview 2, a new analyzer (dotnet/roslyn#44287) will report cases where the target of a global suppression cannot be found. The first thing I would try is opening the solution in this version and looking for reports of IDE0076 in GlobalSuppressions.cs.

That helps. I can see 13 warnings raised by IDE0076 analyzer when I opened the solution in VS 2019 Int Preview (16.7 Preview 4). I found around 35 additional errors from AD0001 analyzer. please see attachment for errors with stack trace. Looks like an issue in IDE0076 and IDE0077 analyzers.
AD0001 errors.txt

Originally posted by @kartheekp-ms in dotnet/roslyn-analyzers#3587 (comment)