I don't know if there is a standard or not. My assumption was always that Safari can share with Safari via iCloud, Chrome with Chrome via Google etc...
I realize that developing a sync protocol from scratch is a big lift But even smaller browsers like Vivaldi have the ability to sync bookmarks with a Vivaldi account. Yes, it will be easy to just adopt an iCloud method and use that but not all good things in life are easy. 🙂
All I can ask is that it be considered. It would make Orion unique amount browsers and would serve a segment that doesn't't like paying monthly fees/distrusts big corps. A small segment sure, but the niche is there. Think about it.