Yeah I also noticed that even though I can accept a calendar invite from gnus in emacs, and the person inviting me sees that I've accepted, my own provider (fastmail) doesn't register me as having accepted in my fastmail calendar.

I've never tried debugging C# from within emacs (though eglot with omnisharp solves all the other IDE needs like goto, see references, renaming and such). I think you're more likely to find help on r/emacs or https://stackoverflow.com/questions/79516308/how-to-debug-c-... or something for that.