I use xBrowserSync for bookmark syncing. The code hasnt been touched in a few years but it still works great. Set it and forget it. There's also an android app - not sure about ios.
I use #xBrowserSync too! I self host the server. It has extensions for Firefox & Chromium. Android app, as you said. But no iOS app. I was trying to make a browser based JavaScript app to use on iOS, but couldn’t finish it it.