tinyraycaster VS pymake

That sounds like a fun challenge. If you're constraining yourself to use as few libraries as possible, I'd go with OBJ [1] for the 3d mesh and PPM [2] for writing images. It's easy to implement a bare bones reader/writer and some OSes (like macOS) can show them in the file browser. Raytracing in One Weekend goes over PPM. There are a bunch of header-only libraries that handle different file formats like stb_image [3]. I usually end up using those when I start dealing with textures or UI elements. I don't use Windows so I haven't used their APIs for projects like this. I'd usually go for imgui or SDL (like you mentioned). tinyracaster, a sibling project of tinyrenderer, touches on those [4]. I liked LazyFoo's SDL tutorial [5]. Good luck!

[1] https://en.wikipedia.org/wiki/Wavefront_.obj_file

[2] https://en.wikipedia.org/wiki/Netpbm#PPM_example

[3] https://github.com/nothings/stb

[4] https://github.com/ssloy/tinyraycaster/wiki/Part-4:-SDL

[5] https://lazyfoo.net/tutorials/SDL/index.php

I haven’t followed this one but I did follow another of his tutorials and that was good, here is ssloy’s tinyraycaster: https://github.com/ssloy/tinyraycaster/wiki

Don't just jump into the source file , read the make file first, from there you'll know how main file is dependent on other files , and start with the .h(header files as they'll give a basic idea what their corresponding .cpp file do and yeah start with small Repos first as they are easier to understand like this one.

I believe this wiki page can walk you through a retro style raycaster engine: https://github.com/ssloy/tinyraycaster/wiki

There's wonky fun stuff you can do with the Make functions. I had some simple mathematical functions working in Make using string length. https://github.com/linuxlizard/pymake/blob/master/math.mk