Microsoft shared mailbox in Apple Mail?

Hi!

I am desperately trying to add a shared mailbox (Microsoft O365 Exchange) in Apple Mail on Mac OS or iPhone OS.

There are a number of instructions on the web and here in the community, but none of them works for me:

1. configure as IMAP account (username: mypersonaaccount@example.com/sharedinbox@example.com). Doesn't seem to work anymore as OAuth 2.0 is not supported
2. Reset the password of the shared mailbox, then configure it as a new Exchange account. Does not work either.

Is there currently a solution for this?

Thanks for any hint