Looks like i was lucky and my bootloader ist still functional.
With the suggested dtb, i was getting stuck on "starting kernel" I assume this dtb is no good for regular x96 (without suffix) ?
However meson-gxl-s905x-p212.dtb seemed to work so far, thernet and wifi both work out of the box, so i assumed its good to use.
I followed your link and followed balbes150's advice on how to start the mmc script
su -
./install-aml.sh
The part that still confuses me is "u-boot.sd"
So far, what i did was to rename the u-boot-s905x-912, that i found on my SD card after burning the image,
to u-boot.ext (follwing OP from this post)
Where is u-boot.sdsupposed to come from?
Anyways, i reburned the image to my SD card, sucessfully booted from that, installed to eMMC (without any Errors) but
boooting wirthout SD still looks like in my first post.