Because it is a commercial product, the safest way to download it is through verified storefronts:
If you are looking for free mushroom-themed software, several official "free-to-play" or "pay-what-you-want" alternatives exist: Save 70% on MUSHROOMAN on Steam MUSHROOMAN Free Download
MUSHROOMAN was developed and published by Pine Games and released on December 17, 2022. It is a multi-genre title spanning action, indie, simulation, and RPG elements. Official Purchase Options Because it is a commercial product, the safest