Mutually authenticated TLS doesn't care about which protocol is being spoken over TLS, so whether you speak HTTP/1.1, HTTP/2 or a Martian protocol you dreamed up yesterday it works fine either way.

NTLM auth is garbage. Google didn't break it, Microsoft acknowledged many years ago that this is trash and you should stop using it, so unsurprisingly they didn't put in the engineering effort to support using this broken trash over HTTP/2 on IIS or Edge.