Note
If you followed this guide before, you might want to scroll all the way down to the TL;DR version of this guide
Somehow, I managed to ”brick“ my Mac mini (2018, Intel) when I wiped its data before selling it online. From the on I could no longer:
- boot the normal Recovery Mode
- re-install macOS using an USB stick
- use the online Recovery Mode, since it always ended up in a error
-1008F