Fails to boot since 4.20~rc1 on various 2019-2020 Mac (Grub doesn't load)

Original report

All earlier Tails versions I've ever used boot on the 2019 16-inch MacBook Pro (Intel).

But 4.20~rc1 doesn't. Grub doesn't load, therefore Tails never loads. Just a black screen after selecting it from the Apple EFI boot menu.

Something must have changed in Tails boot/Grub files since 4.19? (even since the defunct 4.19~rc1 which also boots fine?)

Copying EFI/BOOT/BOOTX64.EFI from 4.19 to the same location on the 4.20~rc1 USB stick fixes the bug ⇒ the problem was introduced by a shim upgrade.

Edited Sep 06, 2021 by intrigeri

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