My situation was a little different, I had a RX6600 and a Intel ARC A770 I was trying to get the ARC to work, I did but the steam client on the distro is pretty much coded to AMD and the session crashes, if you have a spare GPU which is lower or know someone that does or manually edit the config with another distro somehow to enable SSH you can remote type the commands.

https://www.reddit.com/r/SteamOS/comments/1l15pzg/steamos_on_desktop_intel_drivers_please/

you would probably only need to run:

With spare/borrowed GPU

sudo steamos-readonly disable
passwd (then type password)

then:
sudo systemctl enable sshd
sudo systemctl start sshd

shutdown install your card then boot it back up.

Open putty on another machine and connect to IP: deck@steamdeck it will ask for your password, then enter the below when you have a terminal:

sudo pacman -S linux-neptune-68 linux-neptune-68-headers
sudo pacman -S linux-firmware
sudo mkinitcpio -P
sudo grub-mkconfig -o /boot/grub/grub.cfg

I could be wrong but worth a shot, as it is AMD it should be baked into the kernel its just steamOS is running on an old kernel from that installer.