My dad uses https://www.soundjack.eu/ running on a Raspberry Pi to practice with his wind quartet. along with a separate video call so they can see each other.

Its also a peer2peer system, and not easy to set up correctly.

Well, considering that ping times can be still abysmal due to your ISP's incompetence...

Some tests that focus on interconnection issues (ISP to another ISP):

Continuous

To Azure: https://azurespeedtest.azurewebsites.net/

To AWS: https://awsspeedtest.xvf.dk/

One-time

To Cloudflare: https://speed.cloudflare.com/

To Netflix (maybe misleading due to direct interconnectivity in some ISPs): https://fast.com/

Sorry, but 20ms is more than double the amount I can tolerate when playing my instrument.

Even just the difference between local loopback (instrument -> headphones) vs instrument -> USB -> PC -> USB -> headphones, feels like playing with someone continually dragging the tempo down.

I'm sure I could relearn and adapt to >10ms, but this is a far cry from a live experience of playing with others, and I am definitely not alone in my cohort (after trying several low latency remote meetup configurations).

20ms is actually equivalent to playing/singing with someone around 20 feet away from you, on a stage. (Sound travels around 1.13 feet per millisecond.)

Many of us in classical music are doing this all the time. So it's definitely doable. Especially if you have a conductor! Indeed, that's one of the reasons conductors are useful.

But the conductor is exactly what solves the problem, and which one can't use when one is working via Zoom because of latency.

If you don't have a conductor, always, always, always follow the soloist or concert master, which ever one you have.

Listening to yourself on a 20ms delay is a far different thing than listing to someone else on the same delay. The latter is what you experience in every day life all the time as sound travels about 1ms/foot. The former causes a negative feedback loop that will cause problems as you try in vain to effect an impossible correction. https://en.wikipedia.org/wiki/Delayed_Auditory_Feedback

I’ve read that setup was non-trivial. How did you find it?

It is pretty painful to set up, that's for sure. You need to be comfortable with the command line so I haven't been able to experiment yet with non-computer friends. I'm going to try to create some sort of one-liner setup script for my friends to use but I haven't gotten there yet.

There are some good instructions here for different systems.

https://ccrma.stanford.edu/software/jacktrip/

For anyone who hasn't seen it yet - this adjacent project sells a complete unit utilizing this software. As far as I can tell it's just a raspberry pi with an ADC/DAC hat, in a metal enclosure, and some sort of cloud configuration interface. They also publish the details and the pi image if you want to build your own, and subscribe to their cloud plans.

https://www.jacktrip.org/studio.html