No valid bootloader target device found.
For UEFI installation , you must include an EFI System Partition on a
GPT-formatted disk, mounted at /boot/efi.
I just dont have any idea how i need to do this when no os is installed on the server.
What kind of “Server” are you trying to install this on?
The error message indicates that you have either no valid, working disk (defective or no SSD or hard disk) or a new PC (Not a Server!) requiring EFI boot… Here the hardware is not recognized, too new hardware!.
It would not be the first time (even on this forum!) that “before the PC / Server was working” statement was used… And had to be withdrawn, after a RAID check on the Dell Server revealed only defektive disks inside that server…
And I was correct that this is a PC, not a server:
“I just dont have any idea how i need to do this when no os is installed on the server.”…
Please check, if your hardware (Controller, CPU, NICs) are at all supported by RHEL7 / Centos7.
NethServer is based on Centos7 / RHEL7, so only supported hardware on those platforms will run without issues. Centos7 / RHEL7 is about 7 years old, so don’t expect support for new hardware!
Newer hardware is often a problem, and so are PCs using EFI boot…