Tosnic: Thank you for your well-informed recommendations, UhuruNUru.

I will stick with GOG Galaxy for now, since it will eventually get the job done with little hassle. And maybe the GOG staff will fix its bugs along the way, as it does not reliably resume to download after PC standby until I restart the app. I already contacted support about that.

I did not know there were different language installers for the games. I am currently downloading Kingdom Come: Deliverance, which has various language options (fully voiced), but I did not get to choose the language when downloading the installer. Therefore I assume that I will get the installer with all languages.

damjan56445: In case anyone is googling this issue, here's the easy solution. Instead of parsing the link of the game info page - start downloading the file through the browser, then copy the download link from your browser's download page. Works for me:

https://i.imgur.com/62GE6LE.png

Timboli: That works fine for links while they remain active.
Any links not being downloaded die after about 10 minutes.
And any interruption to a download for a link that occurs after 10 minutes since it was added will also die.

At least that is what I have been told is the case ... and unless GOG have changed things again.
GOG's download links never used to die in such a short period of time, and I was able to use a program like Free Download Manager 5 to download the Offline Installer files in a queue.