On 6.12.0-18.18, I managed to get video and keyboard in initramfs by adding these 3 modules in /etc/initramfs-tools/modules:
ps883x
tcsrcc_x1e80100
gpucc_x1e80100
ps883x seems to be needed to get keyboard or video, without it I can’t even reboot using ctrl+alt+delete.
Without tcsrcc_x1e80100, the nvme cannot be found, so rootfs cannot be mounted.
Without gpucc_x1e80100, I have no video in initramfs.
My Ubuntu install doesn’t have full disk encryption, just /home encryption, so I invite anyone to try it with these 3 modules in initramfs. My testing was done by volontarily giving a wrong UUID for the rootfs to grub and see if I had a video output and keyboard. Having these 3 modules in initramfs seems to also fix the “black screen” problem after grub (on the correct UUID), that I could hit sometimes without them.
My Opensuse install has full disk encryption and it works perfectly with these 3 modules.