Bevy is a game engine written in Rust. It targets regular PCs, but thanks to it modularity, it's possible to port it to unusual platforms. These examples replaced the rendering with the one specific to GBA.
Post from @bushRAT in Discord:
Thanks to the ever growing support for no_std in Bevy, I'm now able to use Bevy on the GameBoy Advance! Using the current main branch (which will be included for 0.16!) you can use a crate like agb (and some boilerplate I'm hiding) to write GameBoy Advance games almost as easily as you would for any other Bevy platform. Systems, plugins, resources, queries, the gamepad input API, it all just works. See the attached ROM if you have a GameBoy Advance emulator handy, but I recommend the MGBA emulator as it can also show debug logs (yes, even all the logging just works)
Links to GBA files:
If you have a real GBA or an FPGA console, the author will appreciate if you try :)
Repository: https://github.com/bushrat011899/bevy_agb_test