Floccus Bookmarks Sync
Very flexible, and can sync bookmarks across many different devices and browsers. You can use your own Nextcloud server, or store the bookmarks encrypted on Google Drive or another cloud service. Either way, you know who has access to them, which is a big bonus for privacy.
The desktop browser add-on is mostly set-and-forget and you just use your regular browser bookmarks. For as many browsers as you want. I’ve been using it to sync between Firefox and Chrome since 2020, and while it had some problems syncing early on, it’s been solid for so long I can’t even remember the last time I encountered a sync error.
The mobile app syncs your bookmarks to itself, since most mobile browsers don’t let add-ons access their bookmarks. It took all of 30 seconds to set up the Android version with my Nextcloud, and the initial sync didn’t take much longer. The UI is simple, letting you do the basics of adding, removing, editing and moving bookmarks. They open in your default browser, and you can share a link from your browser to Floccus to bookmark it.