Ahrg! Yes, I only scanned the main page.

I can’t find any mention of the Steam Deck on the Kickstarter page. Any know where the author got the info about the deck support?

The factory must grow!

Pretty unhelpful responses so far. Enter

exit

to exit the current screen and return to a selection of installed OS/Kernels. You should be able to boot normally from there on. Once logged in, try

update-grub 

which should repair your bootloader config.