I use Raindrop, and since i found it, i considered my bookmark system solved. It’s open source, the extension and app are really convenient, everything is saved on the cloud + you can export a CSV or HTML backup whenever you like.
It has a free and paid plan. I use the free plan, it already has unlimited bookmarks and collections. The paid plan has some useful stuff like automatic backups, and an automatic archive of the websites you save, so even if they are taken down you can still check them.
It also has many integrations (IFTTT, Zapier and so on) , which I haven used but this may be useful for you.
In my experience, the best bookmark manager i’ve tried, and i’m surprised it is not used more.