I just use VS code with c# extensions on Linux. It works fine. I also use vim with lsp support for C# sometimes.
If you want more, you may also want to check out Rider from Jetbrains.
Do I need a NAS ?
Do I need a NAS ?
Do I need a NAS ?
Do I need a NAS ?
Unfortunately I can't help you there. I just use plain old kde plasma on Fedora. If your favorite code editor supports Language Server Protocol (LSP), you can probably get it to do code completion for C# one way or another. Vim, neovim, Kate, and many others do.