I downloaded a fresh copy from my GOG account, and can confirm that the MD5 hash expected by ./play.it is the correct one. I get it both when downloading through Firefox and LGOGDownloader.

For some reason it seems the tool you use to download your game installer is silently modifying it, corrupting it in the process. I suggest giving a try to either Firefox or LGOGDownloader to get an unmodified game installer.

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To be sure your previous runs with sudo did not make a mess of permissions in ./play.it temporary directory, I suggest you clean empty it with: (you might have to use sudo to fully delete this directory)

Hello! Sorry for the late answer. I was already downloading with firefox and lgog downloader, turns out that was the VPN that silenty modifying the signature!
Downloading without it just solve the problem, everything works perfect! Thank you!!
Hope this could help also other people

if there was such thing as a perpetual_facepalm then this would be it.