There's always Rider which works very well for .NET stuff.

For older applications, I would consider Mono or WINE if you really want to run it on Linux. We are experiencing the same scenario where we have an application that was built on .NET 4 over 10 years ago and there's a couple of packages we rely on that will not work on .NET 5/6. We have a rebuild planned, but it will be a large overhaul.