there are probably more than one way (i can think of 3) to do what you are intending, but i think i would do this:
if you have automation enabled, you could schedule a daily job to run a data explorer for new sign ups and then pm to a group or trust_level (say TL3 regulars).
this query will give you the new sign-up for the last day:
-- Counts all new users from yesterday
SELECT
(CURRENT_DATE - INTERVAL '1 day')::DATE AS sign_up_date,
COUNT(u.id) AS new_users_yesterday
FROM users AS u
WHERE
u.created_at >= (CURRENT_DATE - INTERVAL '1 day') AND u.created_at < CURRENT_DATE
this will do the last 24 hours from time of query run:
-- Counts new users in the last rolling 24-hour period
SELECT
COUNT(u.id) AS new_users_last_24_hours
FROM users AS u
WHERE
u.created_at >= NOW() - INTERVAL '24 hours'
OR
- use automation to post a query to a secure topic that only a group can see and are set to watching (similar to above) - this might be a slightly less intrusive method than PM.
- you could configure a chat webhook and use the
user createdevent
personally i would use personal messages (or dedicated topic) for this, since chat settings for email notification are set in the user preferences at /my/preferences/email
