This has been a pain point with me over the past 3 months or so in december. I've taken long weekends to wreck this thing, rebuild grub.cfg's from scratch, just about everything to make it work, but it simply doesn't. I've reached the point this isn't my problem directly, but rather some bug. Holiday project gone bad, had to learn grub cfg's just to make it work again. Another of those things you really don't want to know, but some unforeseen circumstance makes you own it.
Rewind a bit, I use a classic recipe for me usually, raid+luks(encryption)+lvm+fs. In this case, no raid, just efi+luks+lvm+fs. The kernel as building it both with 4.19, efi bootstraps just fine, launches grub, launches the kernel, and it just craps out find my encryption volume to unlock first before the root pivot. I can boot ubuntu that works just dandy with their kernel without any deep changes, and arch-based I mod the mkinitcpio.conf hooks accordingly, and still it doesn't work. I've entirely duplicated my build from my desktop, which works fine with raid+luks+lvm+fs, and still it refuses. I can only think some regression/bug at this point, there's no other reason this shouldn't work.
I was debating copying my kernel from my desktop that builds clean and works just dandy with all of the above, which I haven't upgraded in the past few months, prior to my fscking with this laptop and angering me at least. I don't know why, but I'm done feeling entirely guilty/stupid for not being able to make it work, as forums show I'm not the only one. Some sort of regression I suspect that no one but the diehard's that do the FS stack like I do notice, but it has been noticed...
-mb