The original Kerbal Space Program can be found on both Steam and Humble. Its sequel hasn’t yet entered either market yet, but it should fairly soon. The game currently is not on the Epic Games Store. However, it’s possible the sequel might, as it does fall under the “other digital storefronts” guideline.
No surprise for these mechanics
Finally, the third question was about KSP2 possibly heading to Mac or Linux. Well, the answer is: not yet, maybe. Currently, the team hasn’t announced that the game will go to other platforms or operating systems, but will leave the possibility open.
Kerbal Space Program 2 will launch for PC some time next year.
