How much linux is required for the phone to run?

[Subsentient]

Oh I had no idea there were many hoops to jump through. I thought it'd be fun to program a device that only runs my code with a touchscreen and wifi

Yeah it's depressing on ARM except in the server space where ACPI is starting to appear.

If you want that kind of barebones experience, I'd recommend moving up to raw AVR microcontrollers, like the ATTiny85, my favorite. They're a lot of fun, and they're bare metal entirely, no arduino board to baby you. Just 8K of ROM to put your compiled C into. You can get a row of around 10 of them for like $15, then you can fiddle with them however you like.

You could also consider getting into linux kernel driver development, knowledge which would be useful in both ARM and x86 spaces.

How much boot/init knowledge is required? I absolutely would like a touchscreen and either wifi or a modem with 4g capabilities/SMS.
Would it have enough CPU power to run a basic rougelike game written in C at 60fps? Things simple enough that the nes/snes can do with pixels instead of tiles which make those consoles life easier

Ahh, I see. There are beefier AVR microcontrollers that can probably do what you want, but the ATTIny85 is not it. I would look at some of the higher end ATmega family.

Though, I'm starting to think you'd be better off writing such things as apps for Linux on the PinePhone. Wifi/4G support can be accessed easily that way, and you get full access to high-quality game frameworks like SDL2. Why reinvent the wheel, after all? You can write it in C, just like in microcontrollers/arduino. Many applications in Linux are.

[overdrawnfettuccine]

How much boot/init knowledge is required? I absolutely would like a touchscreen and either wifi or a modem with 4g capabilities/SMS.
Would it have enough CPU power to run a basic rougelike game written in C at 60fps? Things simple enough that the nes/snes can do with pixels instead of tiles which make those consoles life easier

Ahh, I see. There are beefier AVR microcontrollers that can probably do what you want, but the ATTIny85 is not it. I would look at some of the higher end ATmega family.

Though, I'm starting to think you'd be better off writing such things as apps for Linux on the PinePhone. Wifi/4G support can be accessed easily that way, and you get full access to high-quality game frameworks like SDL2. Why reinvent the wheel, after all? You can write it in C, just like in microcontrollers/arduino. Many applications in Linux are.

It's more fun when it's bare metal. I'm sure I can easily figure out how to manage the screen and I can live without sound. Input probably not too terrible. However networking is outside of my realm unless I can access it through a library or AT commands.