I used to use Xbrowsersync but switched to Floccus
I found it to be more reliable and I am also in greater control of the sync settings. Plus, it lets you store the bookmarks in traditional storage mediums like Nextcloud or WebDAV, or even a Google Drive. I also like their mobile apps better.
If you need a free cloud drive that offers WebDAV, you can use Koofr. Get 10GB of cloud storage for free.