Never even knew this was there.
https://wiki.koozali.org/Dirty_ToolsWorth a look Brian/JP?
Not sure this what you need though.
So, real time sync is not easy. It is an issue some of the finest IT brains on the planet have struggled with!! File/record locking to prevent overwriting is difficult.
Think about this.
User at location A edits File A
At the same time:
User at location B edits File A
Now we have a conflict. Which one is right?
I have run 2 sites for 14 years using Unison. (I ought to do a Howto).
It is a clever wrapper around rsync.
https://www.cis.upenn.edu/~bcpierce/unison/It can't solve the above problem, but for most use it is fine. You just have to check the conflicts.
My ibays run on a cron every 20 minutes via a script to make sure a job is not already running.
If you are going to have lots of conflicts you need to look at something else.
If you want a full real time sync you need to look for a different solution entirely...
Have a search online for "linux real time file sync"
https://duckduckgo.com/?q=linux+real+time+file+sync&t=fpas&ia=qa