st7789_mpy VS doomgeneric

Are you using C/C++ or MicroPython? I have used https://github.com/russhughes/st7789_mpy successfully. There are actually two/three libraries related to st7789 displays if this I the one you are using. As already commented, please share a link to the display or some more information about it.

The colour being mangled turns out to be an endian difference between the MPU and the display device, easily determined by looking at the code for the display driver, which byte-swaps everything when drawing into the device, unless it's blitting a buffer, when it assumes it's already swapped. Fixed.

I ended up making it work but with no help from LilyGo. There's an awesome repo here that includes pre-compiled binaries for the device, libraries for its hardware peripherals, and some code examples

But as was written somewhere else in the comments and as I wrote myself in the README, the hard work of making Doom more portable was done by the incredible project doom-generic which I forked: https://github.com/ozkl/doomgeneric

It can surely be implemented with a GDNative add-on (3.x) or GDExtension (4.0). Someone on the Godot Contributors Chat is looking into integrating doomgeneric with GDNative, so you can play Doom within Godot :)

You also could alternatively start from https://github.com/ozkl/doomgeneric and all you'd have to do is feed it functions for drawing to the display and getting inputand

Another alternative is to compile Doom to an intermediate representation and a corresponding virtual machine in Lua. Then you build something like https://github.com/ozkl/doomgeneric where you only need to implement a handful of platform specific functions.