Yea Jetbrains Rider is fantastic. I'm assuming the parent never tried it. Seeing as it is essentially IntelliJ the comparison to Java tooling seems ironic.

I second this. .NET core works flawlessly on Linux and JetBrains Rider (and on Mac, which is what I develop on). The standard libraries and ASP.Net core are really well designed and a joy to work with.

Seconding Rider. I use Windows and still prefer it to VS.

On an IDE written in Java....

Rider is a solid mix of C#, F#, Kotlin, and Java (and likely more). The R# engine is a very large .NET codebase, and the F# plugin to that is written largely in F#. So it's a little more complicated than whatever the shell is written in.