[frostschutz]

If you upload the tar you made somewhere, I can check if it's correct.

Well, it would be better to use the provided tar file as is. Certainly there is an unzip for Mac that doesn't force you to unpack the tar as well?

I'm not familiar with the Clara, if you have opened the device anyway to get to the SD Card slot, you might be able to disconnect / reconnect the battery, if it's a plug like was the case with old Kobos, and not soldered/glued on.

It's also possible for the battery to drain, if it was stuck in a script somewhere. The Memory Mod does an infinite loop waiting for you to replace the SD card, but that's with sleep statements so it should not eat power. However there may still be Kobo services in the background and who knows what happens there, so maybe try charging it as well.