Hello,
As much as we would love to, it's more a desicion from our publisher. The game has some systems that require a complete rework to support this platform, unless you want a version on itch.io without Online ProtoCorgi Maker, Online Highscores and achievements.
For our next games, we plan to have fewer online systems and focus better on other areas to support itch.io better.
As a note, the Steam version has Linux support.