Mario663

No, the only output is to the screen

The only suggestion I have on the usb burning tool is to try different versions.  I have found that with some older TV boxes, the latest version sometimes doesn't work, but an older one will.
One other point I will mention is to have the box disconnected from power when you are trying to connect to it with the burning tool (it should get power over the usb connection) and to try different usb ports on the box.

Did you tried this? https://docs.armbian.com/User-Guide_Fine-Tuning/#system-language

I don't know what the problem is because as I said, you didn't capture the important part of the install-aml.sh script run.  But I also did say the following:
If you want a valid test of installing to emmc you need to restore the box to the original android firmware and start from there.  And it may still not work, but that is the starting state the script expects and the only thing that is tested.

I downloaded the following:
Armbian_23.02.0-trunk_Aml-s9xx-box_lunar_edge_6.1.4_xfce_desktop.img.xz
dumped to a memory card.  
Mounted the card and modified the extlinux.conf
copied u-boot-s905x-s912 to u-boot.ext
unmounted the card, and put it in the MXQ PRO
Booted just fine. 
Logged in and ran the command:
$ sudo su -
(password)
# ./install-aml.sh
 
Installed to eMMC
Process works fine.

WordPad is even worse. Use only Notepad++ or follow @SteeMan's advise (don't allow the sd card to touch a windows machine).