Currently $4 on GOG. Less appealing than "free", but quite cheap, money goes to the indie dev, and most importantly, you get that copy for as long as you want it because it's DRM-free.

Might pick it up there myself. It looks solid! (And has a native Linux version, albeit targeted at Ubuntu 16.04 and 18.04.)

Edit: Leap of faith. Decided to pick it up on GOG. If the Linux version is too old, it'll definitely work with WINE.