At work we've been slowly pulling code out of our WebForms monolith. That's still on .NET Framework, and will be forever until we're done killing it, but we can use recent VS and MSBuild with it and we use C# 9 as well. Business code generally works copy and paste in .NET Core, so there's a really good path to migrate to newer stuff, especially with .Net Standard 2.0 being a thing.

gRPC is really fast and we have the WebForms monolith call into .NET Core services now so we can improve the back-end without dealing with so much ASPX crap.