It doesn’t work for me, perhaps because I’m using gravity forms for user registration.

That could be why. There’s no reason @shanebp‘s solution won’t work on a default BuddyPress install

It doesn’t work for me, perhaps because I’m using gravity forms for user registration.

That’s possible!

I haven’t tested yet. There is an activity entry for ‘new_member’ that gets created. Not sure if that is when they first login or or first activate.

new_member is an activity type. It’s created when a user activates their account (at the point at which the bp_core_activated_user hook fires).

I’m not aware of a hook that fires on first login only. A way around that might be to add a meta key to the user’s meta on registration and then check for that on each login attempt. You’d need to remove the key after you’ve performed the check (if the key exists). If no key exists, then the user has logged in before. Just thinking out…[Read more]

In my case, I would like to auto reassign to a different ID when a user deletes their account.

I think that functionality only happens when the member is deleted by the administrator in the WP dashboard. Posts aren’t reassigned if the member deletes their own account via the front end.