I recently got this second hand nvidia shield, and heard lineageOS was compatibile. I have access to this guide https://wiki.lineageos.org/devices/foster/variant1/ but I'm having some doubts about its compatibility. Can someone confirm?
I don't have experience with shields but from my mourned I suggest you check weather you have the original firmware before proceeding and know how to install it. It'll be less of a headache when you mess something up. Also check xda. Good luck!