Hi, so this looks awesome! Will you be supporting Linux?
To be honest, if you simply added a Linux build to the purchase with the caveat that it's completely untested even that would be a great step. Then if it works out of the box the problem would be solved, and if not then no big loss 😄 I'll also add a +1 to the number of people who'd be willing to debug should that be the case!
it's very easy to set up a virtual machine for testing, if that helps. no need to have an entire machine dedicated to linux. you may also find that technically-inclined players will be willing to help you troubleshoot problems.
I can understand your point and of course you're not obligated to support any particular platform though. I agree with the other poster that supplying an explicitly unsupported linux build would probably be good enough. I will probably roll the dice and buy the game, since another player said the windows version worked via wine.
it runs very well in wine! just download the windows version from the download page.
for a raspberry pi build there would need to be a linux build. depending on what engine dave used i think an android/iOS port would be fairly simple, though it would also require them to go through the process of applying to list on the respective app stores.
make sure wine is installed first. if you're on ubuntu the command would be "sudo apt install wine".
then download the windows version of the game from the website and unzip it.
open a terminal and "cd" to where the game files are, then run "wine Mixolumia.exe".
hope that helps!!