I run a small SaaS side hustle where the core value proposition of the product - at least what got us our first customers, even if they did not realize what was happening under the hood - is, essentially, an implementation of NTP running over HTTPS that can be run on some odd devices and sync those devices to mobile phones via a front end app and backend server. There’s some other CMS stuff that makes it easy for the various customers to serve their content to their customers’ devices, but at the end of the day our core trade secret is just using a roll-your-own NTP implementation… I love how NTP is just the tip of the iceberg when it comes to the wicked problem of aligning clocks. This is all just to say - I feel your pain, but also not really since it sounds like you are dealing with higher precision and greater challenges than I ever had to!

Here’s a great podcast on the topic which you will surely like!

https://signalsandthreads.com/clock-synchronization/

And a related HN thread in case you missed it:

https://news.ycombinator.com/item?id=39298652