Thanks for reporting, it looks like Manual leaning isn't functional in Firestorm sadly. We're working on a fix.
Original Post
https://www.reddit.com/r/BattlefieldV/comments/bs1kk6/is_manual_leaning_disabled_in_firestorm/
Will this be a hotfix?
I doubt, since this isn't really a critical issue.
Manual leaning is not in Firestorm yet. It is on its way and you'll have it in a couple of patches time.