Basically in the same boat. If you haven’t looked recently, the container support in Windows is getting much better - including prod support for Windows worker nodes in Kubernetes 1.14. But just using Docker with gMSAs was a big help to our CI/CD and simplifying/standardizing deployment of our apps which are a mix of legacy ASP.NET, WCF, and traditional Windows services.

If you can target at least 4.7.1 you can use configuration builders [0] to use environment variables/json/cloud parameter stores/etc to modify legacy web.config or appsettings without code changes. You can also use the .Net core config libraries directly in legacy .Net apps if the devs are willing.

[0] https://docs.microsoft.com/en-us/aspnet/config-builder