[berthaboy73]

OK – I’ve just found this:

add_action('bp_core_activated_user', 'kleo_add_member_activity');
function kleo_add_member_activity($user_id)
{
add_user_meta( $user_id, 'last_activity', date("Y-m-d H:i:s"));
}

on https://seventhqueen.com/blog/buddypress/show-users-members-directory-right-account-activation.html

So will just have to import user data again (using https://codection.com/import-users-csv-meta/) and modify the code to add that activity record.