[nAwYz]

I had the same problem, it has something to do with Plymouth, if you use the classic console boot it works

[newnewpdro]

Oh, so you can still boot, they just don't support (or have broken support for) DRM_IOCTL_MODE_CREATE_DUMB.

But what does that have to do with encrypted root? Just plymouth not being available for the LUKS passphrase entry?

I'd expect you to be able to get around that fairly trivially by disabling plymouth, LUKS works without it in any initrd I've encountered.

[yjftsjthsd-h]

That effectively is breaking the boot process. Of course, you may be able to tinker with it in order to make things work again, but you have to do that.

[newnewpdro]

It's not a breakage specific to whole-fs encryption, which is what didn't make sense.