I moved the topic to “making liveness”, it seems to fit better, hope that’s OK!
Yes there have been a few efforts. TopClock had a lot of eyes on it but went nowhere really.
PTPd is a general protocol for syncing system clocks on a LAN (similar to ntpd, but that’s for WANs), which is part of the battle, but you still need a protocol for sharing tempo relative to that.
Various live coding systems have their own protocol for syncing.
Most promising for pan-system sync are EspGrid from @dktr0 and Link from AbleTon.
EspGrid is designed with live coding in mind, is free/open source, and is easy to implement. There’s an ongoing but slow effort to get it working reliably cross-platform. It feels like it’s nearly there but there are a few bugs in the way of being fully usable in the field (please do correct me David).
Link has a lot of commercial support, and one of the implementations (C++) is available under a GPL license, but it’s not really a free/open source project - they don’t take patches under the GPL, so that they can maintain a proprietary license as well. Nonetheless, it works very well, is getting core SuperCollider support and makes collaborating with a wide range of software straightforward.
There’s also systems like the multi-user Troop and Extramuros editors (I think both work with foxdot, tidal, supercollider, sonic pi) where all the code gets run on one machine, getting around the need to sync at all, as long as you’re all running the same language.