I would definitely be up for testing some new firmware.
That’s great! Do you happen to have an AVR ISP programmer at hand? I have an initial implementation of a setting to not output the test pattern when there is no input. Just need to figure out how to allow the user to control it while the device is running, instead of hard-coding the setting in the firmware. Currently, in the test firmware, pressing either one of the buttons or both at the same time are mapped to input change / smoothing / save settings, respectively.