I usually use the count on the /users page
/users 22051 users
On my localhost set-up I have some discrepancies.
I know I created 54 accounts. (in addition to system and eviltrout that I didn’t create)
SELECT MAX(id) FROM users gives 54
But my /users shows 51
my /about shows 45
my dashboard per TL adds up to 45
and my dashboard new users all shows 45
I have 3 suspended and 2 blocked users, 1 account never authenticated and 2 never made a post (but 1 has Liked) and 1 has posted only in PMs.
AFAICT anonymous accounts aren’t in any count.
So it looks like /users counts members that have posted in public topics regardless of member status while elsewhere certain accounts aren’t included in the tally.
Or it could just be localhost install funkiness.