Yes 
I made it.
As said before, the problem is that efibootmgr of Garuda Linux is not able to configure the UEFI NVRAM entry.
However, this does not necessarily have to be done via the Garudu Linux.
So I put a Debian Live System on a USB stick and booted from it. From there I made the NVRAM entry with the efibootmgr which worked right away and it also booted the grub boot loader. Since grub was not configured yet, I put the Garuda USB stick again to fix the boot mananger configuration and now the Macbook Pro boots the Garuda Dragonized 221019.
