I think this is supported.
We are using NGINX with its core Stream module to receive HTTP/2 encrypted traffic, and loadbalance it (with random or least_conn) algorithms -- to each of our backends.
Traffic stays encrypted end-to-end, and it remains HTTP/2 (because the Stream module works at TCP level, not http so it does not care http/2 or http/1 is used).
It seems that in the ticket [2] that you mentioned, the commenter at the end is asking exactly for this. And that works well.
It is called often 'pass-through proxy'. The article here explains how to set it up
https://serversforhackers.com/c/tcp-load-balancing-with-ngin...
We loose information about the Web-browser's IP address at our backend. For for privacy-enforcement reasons, we actually do not want to have it at our terminating points (our backend apis). And also, if we ever need it -- I thin this can be enabled with the proxy protocol.