Is there a way to make MP’s actually really private ? Where an admin can not access other members MP’s unless there’re invited with a flagging or a tag ?

Yes, check Discourse Encrypt (for Private Messages)

Сделайте личные сообщения действительно приватными

Falco (Falco) 03.Декабрь.2020 15:12:00 2

Тема		Ответов	Просм.
How to make it so that admins are not able to view private messages of their users? Support	10	1991	09.05.2019
How alert if admin/mods read users PM? Support	9	1317	14.02.2022
Are PMs truly private and not crawlable? Community Building	4	1313	16.08.2020
Can I view private messages as an Admin? Support	13	5280	14.09.2020
Can true private messages be implemented? Feature	28	5784	09.03.2020