I've used JamKazam (https://www.jamkazam.com) a few times recently to play folk music with some friends. The sort of music we play relies very heavily on listening to each other and improvising, and surprisingly it _just about_ works on JamKazam. It's certainly not perfect, but we're not going to be hanging out in pubs together any time soon.
The important number is round-trip latency, and we found that around 25ms is good enough (we're all quite used to playing with people of varying time-keeping ability anyway). I think there's scope to improve on that using a library like Roc (https://github.com/roc-project/roc) where you can target a specific latency. I've been meaning to play around with it, but to be honest I'd rather be playing music :)
The important number is round-trip latency, and we found that around 25ms is good enough (we're all quite used to playing with people of varying time-keeping ability anyway). I think there's scope to improve on that using a library like Roc (https://github.com/roc-project/roc) where you can target a specific latency. I've been meaning to play around with it, but to be honest I'd rather be playing music :)