Sharepoint - 400 Bad request when loading sharepoint site from client

The issue here was that VS created my console application as a .net core app, which as far as I'm aware does not work with the Microsoft.SharePoint.Client library.

I tried this previously in VSCode and it immediately threw an error saying the libraries are built for a different framework - I guess VS somehow doesn't know how to report that error.

After creating a new app using the standard framework, it seems to be working.