Hmm so I did that part right. I did a ls -l on /dev/disk/by-partuuid and have the same partuuids as they are set in the grub.cfg file.
Im wondering what’s going wrong because now it should be able to boot. Yesterday evening I dd’d the .uefimg to a usb drive and it booted with no problems. I tried it with /dev/sda and /dev/by-partuuid configurations and both worked without any other configuration steps.
Edit:
What I noticed right now is while running the .uefiimg from a live USB drive it don’t find the SSD either. lsblk and /dev/disk/by-partuuid only showing the usb drive. Do I have to install some package or reconfig the kernel? I looked into the Kernel config and everything should be set properly.
I tried setting this up to autogenerate the UUIDs but that caused cache issues in Yocto since they would be different on each invocation. As long as they are all different that’s all that matters.
I finally managed to get my SSD being detected. It was no mender problem as you guys said. I had to switch from AHCI from IDE in BIOS settings which wasn’t that easy since the BIOS of my board has almost no configuration possiblitys. But thanks for your help anyways!!!