I can also recommand WASM-4 (https://wasm4.org/), that has even more constraints (screen resolution, color count, …) and that you can program with your language of choice, as long as it can compile to WASM (eg. C, C++, Rust, probably Nim…).

What I don't like about these fantasy consoles compared to real ones is that they don't put any limits on computational power.