I will try to modify the entry on itch.io, meanwhile you can try and download both files (SomethingRemarkable.Windows.exe and the pkg ) from Bin on the github repo
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https://github.com/alex9099/SomethingRemarkable/raw/master/Bin/SomethingRemarkable.Windows.exe
https://github.com/alex9099/SomethingRemarkable/raw/master/Bin/SomethingRemarkab...
Download these two files into any folder. Then just run the exe. Might take some time to launch (took like 20 seconds for me on Windows 10 for some reason) but should work.