[BUG] Installing LMDE4 "Debbie" with another language than English fails

[FeedbackReporter]

Provide precise and relevant information

As already mentioned here https://forums.linuxmint.com/viewtopic.php?t=320829 (and seemingly totally ignored), installation fails if English isn't the chosen language. The installation quits with the following error:

'ascii' codec can't decode byte (the following position depends on the first non-ascii letter in the chosen language)

I tried today to get Debbie installed in German. Same issue. I tried changing just the keyboard after finding the forum thread. First to UK English, then to US. Both didn't help. After changing all language entries to US English, the installer would go on (probably UK English would also be okay, I didn't have the time to try it).

Provide stack traces for crashes
Sorry, I didn't think of going for dmesg at that time. But after all, forums on the internet are full with that error message.
I will try to get the same thing on my broken laptop in the next days. I will report.

Explain your expectation
The installer should be able to go on, no matter which language the user chooses. Just like the "normal" Cinnamon installer.

Be patient and pleasant
I hope I was, I never try to be "grumpy" or to insult someone. And sorry for any grammar mistakes, English isn't my native language :)