I personally have needed to sync something between 3 and 6 devices over the past 5 years on a daily/weekly basis.

I invite you to figure out how to algorithmically figure this out in a general case without needing Git Merge levels of complexity for data structures far more complicated than lines of code. Peer to peer device merging of arbitrary files for n > 2 conflicts.

The answer - the algorithmically simple and correct answer - is to have a central hoster and the devices operate as clients. And if you have a central hoster, you now gave yourself a job as sysadmin with requisite backup/failover/restore with data management responsibility handling the decade+ case. Or I could hire a central cloud company to manage my tiny slice of sysadmin needs and _not_ have a part time job at home just dealing with file management and multifile merges.

All models that are "I have a laptop and a backup hard disk" are _broken_.