In the thread from a year ago, it was mentioned that the problem lies with the Developer, where the game cannot be downloaded due to misconfiguration.

I'm begging Itch.io Desktop client to recognize this error and either use a normal http download stream, a WebView of some sort or at least a LINK to the download location so I can use an external browser.

I've bought the Bundle for Ukraine and feel bad for complaining, but there's like a lot to do (for which I'm grateful) and on the other hand this problem seems to be present for quite some while now, when the Desktop client has all the info it needs to provide a better user experience. Now it shows a cryptic error. Pseudo code: IF drop down list.empty SHOW apology message + manual download link.