Welcome to the community!
I’m afraid what you found in the linked thread is still true today: our extension still does not support .NET Core 3.x. We did spend some time on, discovered that it’s a bit more complex to do than we had thought, and then haven’t made further progress. Our .NET expert is on holiday at the moment, I will notify him of this thread and he can provide more up to date information.
In the meantime, there are a few things we can try. To make develop the main branch, please follow the workaround explained in this other thread. Once that’s done, I’m curious if after running an analysis, and you go to the Code tab, do you see correctly the source code files where you expect issues to be reported. Please let me know!