I've hit this issue with the linux-image-5.14.0-1-amd64 (5.14.6-2) that has made its way to testing this week; symptom is grub never shows anything after the loading the initrd message. earlycon=efifb and earlyprintk=efi didn't give any extra output. mem_encrypt=off resulted in a successful boot.
Hardware is a Ryzen 3 3500U laptop. It seems like this is a potential interaction between the memory encryption and amdgpu? J. -- ... "What's the philosophical difference between a killfile and the automoderation?" "A killfile throws away good posts. Automoderation throws away bad posts." -- Jonathan H N Chin to Calle Dybedahl