After Aparslan's comment about version mismatch, I tried to rollback my C# and C# dev extensions from current versions to previous versions (C# Dev - v1.50.51 & C# 2.90.60) and the issue got fixed. IDK, but according to dotnet.microsoft.com, I'm using the latest version. And 9.0.9.sdk110-1 is the latest version on arch repositories.