Tried to start the Windows executable, but Windows Defender pops up and blocks it as they don't recognise the publisher.

Anyone else having this issue?

Windows Defender is garbage.  You should strongly consider using a better/alternate security product like MalwareBytes AntiMalware and similar software.

Hello, thank you for reporting this issue.  We'll investigate and try to find a solution.
If you're willing to help us with more information about your system please write to info [at] selvainteractive [dot] com so we can follow this up.

Thanks!