https://www.instructables.com/Make-your-own-cellphone-from-scratch/

So I'm trying to make a diy phone to hide from glowniggers. The above phone is pretty cool, but it uses a 2G module. What board do I need to make a 4G phone? Preferably one that's compatible with a fun LED display like that. I need a board and microcontroller presumably or all of it on one board.

Tbh, it the linked project, I'm not really sure where the microcontroller even is.