As I simply understands HTTP2 is m:1 pattern where you put m logical connections into 1 TCP stream
Is it possible to do m:n pattern in http2?
m streams are demuxed into n connections for better reliability, because often one single TCP breaks all h2 hangs.
It would be possible, but in practice it is not done.
Browsers especially try hard to open just one connection to a domain, and even reuse the same connection for different subdomains if they can figure out that it resolves to the same IP address and same certificate.
Other clients may implement a m:n scheme (for example, Jetty 9.4.x HTTP/2 client does - disclaimer: I'm the maintainer).
The problem of choosing a good n may not be trivial, and it risks to go back to HTTP/1.1 6-8 TCP connections per domain.
Since each connection would be multiplexed anyway, the failure of a single HTTP/2 connection would be worse than the failure of a single HTTP/1.1 connection (because it would fail multiple requests rather than just one), so I guess that it would not make that much of a difference with respect to a single HTTP/2 connection.
Google's QUIC protocol aims at resolving this issue since it is based on UDP and has built-in in support for connection migration (i.e. switching from WiFi to mobile network).