Http/2 and websockets not working

Modern browsers are requesting http/2 connections but the websocket code in jitsi meet does not seem to support this.
I can access the websocket url using http/2 but not with http/1.1 which is the wss request from the javascript code. my firefox is 84 and chrome is 88.

Did anyone managed to get this to work?
I am now disabling websockets again because of this systematic failure.

web_1 | 195.135.251.189 - - [09/Feb/2021:18:11:38 +0100] “GET /xmpp-websocket?room=test HTTP/1.1” 403 284 “-” “Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Firefox/78.0”

The http/2 call from the browser works:

web_1 | 195.135.251.189 - - [09/Feb/2021:18:12:19 +0100] “GET /xmpp-websocket HTTP/2.0” 200 152 “-” “Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Firefox/78.0”

I have similar problems:
every time a xmpp-request is done via http/1.1 i see a 101 http-result code in my nginx-logs and prosody logs client connected, authenticated as random-string@guest.mydomain and 1-3 seconds later the same client as disconnected again.

This leads to the user seeing a started meeting (without any other participants), while the client has not joined the meeting (nothing about the random-string/userID in jocofo.logs).
Most of the time one reload in the browser leads to a proper connection.

Only about 5-6% of all requests to xmpp-websocket are done with http/1.1.