Sync is really completely broken. I’ve tested Brave months ago, but did not stay as the (beta) sync was completely unusable.
Now I am back. Sync is not longer beta according to the menus. But it still does not work reliable. Created my sync account yesterday on my MacBook. And then synced successfully to iPhone and iPad. Afterwards i moved some folders on MacBook. This change never reached iPhone or iPad. This morning I added a Windows PC. This also got all bookmarks, not including changes I did after initial sync. I moved the same folder again and also added some new test bookmarks. No sync to no other device. I removed my iPhone from the chain and re-added it. All I got was the result of the initial setup yesterday. None of the changes is reflected.
So for me it looks like changes never get synced out to the Sync servers. Regardless of OS as neither my Windows changes nor my MacOs changes seems to get synced out.
I really like Brave and would prefer to use it as daily driver. But not having a reliable bookmark sync is a showstopper for me.