I was messing around with trying to get https://github.com/seblyng/roslyn.nvim working with VB.net. All I had to do to get the LSP to work with VB.net was to add a one liner in CodeAnalysis.LanguageServer.csproj: a project reference to CodeAnalysis.VisualBasic.Features.vbproj.
This is extremely useful to me, and I was wondering if there was an explicit design decision for omitting VB from the LSP? I'm assuming there's a reason behind this, but that one reference allows me to get what seems like full LSP support for VB.net
edit: Working concept in a fork I made here: https://github.com/misterkiem/roslyn-plusvb . I made other changes to get it to build in my environment, and to get it working for Mason, but that shouldn't be necessary. All that's necessary is the one project reference