Glo Caught in update loop after reset

[AleXSR700]

Hello everyone,
after my mum switched to a new device, I wanted to give e-Readers a try.

I reset the Kobo Glo and then connected it to Kobo Desktop App. The Kobo Desktop then downloads an upgrade which I can see is copied to the reader into .kobo\upgrade.
After entering my Kobo account details the setup gets stuck claiming I have no internet connection. Sounds plausible since the reader is not connected to Wifi but instead to my PC.

But when I remove the Kobo glo it automatically starts updating and then, after the update message, the screen goes black ith blinking white lines and then the screen goes "white" with blinking black lines.

I tried multiple times aborting these blinking line upgade screens by doing a factory reset but the exact same thing happens everytime.

Does anybody know why?

The reader still seems to have firmware version 2.x. Latest seems to be 4.x.
Is there an intermediate upgrade step needed or something?

I tried formatting the external SD card but still the same issue.

Thank you for your suggestions

Alex