Hi all,
I made a custom firmware for ATmega32U4-based keyboards.
https://github.com/marcv81/umk.
The features set is minimal: anything you can do with a regular keyboard + remapping keys + layers. On the bright side it takes less than 3kb and the matrix poll rate is close to 2kHz.
Although it is my daily driver casual users would be better off with a mainstream firmware and a strong community.
I'm sharing in case some of the tinkerers here find it worth having a look at. The code should be simple enough for any developer to understand and experiment with, which I believe is the main strength of the project.
By the way, I'm not looking for contributors: the firmware has all the features I want already. I'm unlikely to accept PRs other than bug fixes. This said feel free to fork or reach out with questions and comments!
Cheers,
Marc.