I was thinking of more public type forums where random people are all in a room
Jamulus has both public and private servers. There are some public servers with a large amount of spaces and welcome random people to join, there are also servers specifically set up for ensembles to practice. Choral groups in particular have been making a lot of use of it to rehearse. The prevailing etiquette is that one should not barge in on a piece as to be disruptive, rather wait for a break and ask.
I've seen some Jamulus public servers that come close, though they tend to be pop or jazz focused. Haven't spotted piano focused servers, but that is not stopping anyone from creating one.
It works well and pretty much eliminates latency, beyond what you'd have anyway if you were spread out across a large stage.
As a 28 year old boomer, this blows my mind. Back in my day, there was always latency in internet calls. I wonder how they do it.
They eliminate error checking in the transmission part of the cycle.