I’m using a NextCloud server with Floccus installed on all my browsers. Floccus syncs the bookmarks to the Bookmarks snap-in in NextCloud. It takes some fiddling to get it all syncing properly (or used to, it feels very improved now) and I gotta say it has been a long time since I thought bookmarks were useful, but I like this solution a lot.
It works across anything I’ve tried that takes Firefox or Chrome extensions, and it’s all self-hosted.