Steps to reproduce:

I get Newsletters or Ads, most (due to law) have some sort of "unsubscribe" link below

Actual results:

There is no easy way to unsubscribe. I mean, there is the link, but its not as easy as...

Expected results:

on Apple Mail and Nextcloud I saw this button to unsubscribe from Newsletters etc.

I think it scans for "unsubscribe" "abbestellen" and all the translations, and uses the link after that linked for the unsubscribe button.

Having such a button is completely non essential but really nice for UX. It feels like a mail client that helps against Spam.

There's a List-Unsibscribe header that somewhat eases this for clients, since it gives a machine readable format on how to unsubscribe. I would assume https://addons.thunderbird.net/thunderbird/addon/unsub already works somewhat like that.