Why no Mac Version like in the original Ultra Star games?

[Bacchus]

I would buy it right away, I there was a version for MacOS. Been using Ultra Star Deluxe/Play for a long time on my iMac, would love to make the switch.

[kalixdev]

Primary reason is that there is not enough manpower to support multiple platforms.
Technically it would be possible to also release Melody Mania for macOS.

But the priority was chosen to create one high quality product for Windows, instead of 3 low quality products for Windows, macOS, and Linux.

Furthermore, Windows users are with over 90% by far the majority on Steam ( https://store.steampowered.com/hwsurvey/Steam-Hardware-Software-Survey-Welcome-to-Steam ).

That said, a macOS version might be possible in the future.