For both beta’s I keep getting invited to join through the console.
I opted in for Steam I do not own an Xbox one or Series X
Been having the same issue as well.
I signed up and was opted in for both systems. I got a notification through the Xbox app that I was able to try the test flight but it didn’t mention which system. I have not got an email and cannot find a Steam key anywhere on my Halo Insider page. I have been told the Steam keys should be there.