How to re-enable Brave sync
Due to crashes reports, brave sync has been temporary disabled since v1.3.113.
You can re-enable sync since v1.3.118 by opening
brave://flags/#brave-sync (you need to manually copy & paste this link).
Instead of the default option, just select Enabled, then restart your browser as requested.
Once Brave is restarted, Sync should work as intended. If you experiment bad behavior, restore the flag value to Default.
More information about why Brave has temporarily disabled sync can be found on this official post.