What to do with dialog saying “darktable” can’t be opened because it was not downloaded from the Mac App Store: This bundle supports macOS versions starting with 10.7 (Lion) running on 64 bit Intel architecture. Right now this means for the stable package: The OBS allows packagers to provide packages for multiple Linux distributions.
Check your package manager or software center. If your unix-like operating system is capable of running a graphical session, darktable is likely available. Installation notes Linux/Unix Binary Packages From Your Package Manager