If you want the instances to sync, you just need to sync the directory. (I currently use nextcloud sync for this, but in the past I used synching and before that btsync)

If they dont try to modify the files at the same time (with sync delay) there won’t be any issues. If they do grow out of sync, you can fix pretty easily with db repair.

I mean people said this about SponsorBlock, but it turns out you can crowd source the timestamps… If you built an easy enough UI.