Question/suggestion about performances

I see in
that the output flow is made of K*(K-1) streams.

Is there not a possibility to use all users or only some of them as repeaters…?

That is, any user would receive K-1 flows and send 1 flow to server, but send too 1 or more flows to some other users, depending on its own capacities in CPU and net bandwidth.
This would relieve the main server of the equivalent resources allowing to exceed the current practical limit of 35 users… All this would have to be organized by the server as a great conductor…

First you are underestimating greatly the complexity of a hybrid server/mesh design.
Second and most importantly you are overestimating the advantages, because for one, a browser is not a true operating system and never was intended to be a server, (this is really important as it’s a real time problem and delivery time matters greatly, and then the upload bandwidth of many home connections is between miserable (ADSL) to poor. Theoretically fiber has no technical restriction like ADSL and initially in my country many fibre users had 100Mbits upload or more, but I have come to realise that many now have a sharply asymetrical performance and have truly asymetric fiber. For some reason ISP are now severely capping upload capacity for fiber users at least in my country. So even if it was made to work (totally irrealist) it would be useless in many cases.
In short, no, there is not a chance.

Mmm, in fact, I do not estimate it at all : I am not implementing it, I am dreaming it. Sure, either it is possible in js (I do not know), either it is possible to propose some “jitsi repeater” that user decide to install… In fact, every bit “repeated” would relieve the server even if it is small. Ok, I should not dream…