Hi @underdog welcome to the forum.
For help with Easy Installer, you will have read the troubleshooting guide please can you upload a log.
In the meantime I will point you to this Windows thread where myself (with no Gigaset) and a new-to-gigaset user learns about the bootloader on your device. Please be sure to read to the end and the final (hidden) photo! 
I chose this just from the trace you chose to show us.
adb devices will answer when you are in Recovery mode,
fastboot devices will answer when you are in Fastboot mode.
Bon chance 