Hi Vlad and everyone else,
I'm also very interested in this subject, and I understand it's a complex issue, and depending on how it's tackled, it could mean a lot of work.
Since this topic speaks about 2 different things, Bookmarks & Self Hosting, I'll separate them for now.
Right now, 2 of the most commonly referred-to methods for syncing bookmarks between browsers seem to be 2 extensions, xBrowserSync and floccus.
I've tried the Firefox and Chrome stores versions of both, and couldn't make them work on Orion.
Of the 2 floccus seems the most interesting and the most mature, giving a lot of choice to the user, and the ability to self-host the Bookmarks.
xBrowserSync, on the other hand has E2E and you can either use one of the available public xBrowserSync services or run your own.
I don't know what stops both extensions from working in Orion, and how difficult it can be to make it work.
One last thing I want to mention is that a lot of people speak about knowing if we can trust a company (like Apple, Mozilla, etc.), and I think the best situations are when trust is not necessary, meaning as much E2E as possible.
If I have encrypted files on iCloud Drive, granted Apple knows already a lot of information, like who is putting those files, what clients are used, when, etc. but it is still a great to have encrypted files.
I have heard of software like etebase to help with that, but I have no idea how hard it is to implement and to use, just food for thoughts!
Best regards,
Charlie