Basically I am using mull on android and librewolf on linux.I want to use firefox sync or something line that for syncing.So how good Firefox sync is, in privacy point on view.
I am not anonymity paranoid I just want privacy so basically what do they collect and for what?
I started using Librewolf a few days ago and they recommend xBroswerSync in their very short list of recommended addons. This has been working fine for me although sometimes all my bookmarks disappear but that soon sorts itself out after a sync.
There's not an extension but there is an app (available as apk or from F-Droid/Google Play). The app contains all your bookmarks and easily searchable, you click on the bookmark and it opens in whatever your default browser is, in my case it's Fennec. Not as easy as just typing in the search bar in the browser but it's a small cost for not having a Mozilla account (I've nothing against Mozilla but the fewer big organisations who have my data, the better).