Google shutting down Bookmarks

I just saw this message this morning. So Google shuts down yet another really useful web service, forcing the rest of us to scramble in search of an alternative.

Once again, the point is hammered home: If you aren't paying for the service, then you are not the customer, you are the product. And cloud-based software means it can be taken away from you at any time and you will have absolutely no recourse when it happens.

And now I need to either switch back to using locally-stored bookmark files, create a web page somewhere to provide remote access, or switch to a different cloud service and risk them in turn going away.

And now my question to you: Is there a good alternative? Ideally, it should offer:

• Stored on an Internet-hosted server so I can access bookmarks when I'm away from home
• Cross-platform. Should work with multiple browsers (especially Firefox, but ideally others as well) and on multiple platforms (Windows, macOS and Linux)
• Have a convenient browser add-on so the bookmarks can be presented as a menu somewhere (ideally on its bookmarks toolbar)

I know Apple supports shared bookmarks via iCloud, but it only supports their Safari browser on Apple devices. Firefox offers a sync service, but it only supports Firefox.

If you know of any other good alternatives, please let me know.