linuxmuster-import-devices doesn't differenciate between OPSI and OPSI via UEFI (regarding DHCP filename).
accordingly /usr/lib/linuxmuster/constants.py sets OPSIPXEFILE="linux/pxelinux.0" and not "linux/pxelinux.cfg/elilo.efi" too. Which would be correct for opsi via uefi.
It's not possible to image devices with OPSI via UEFI because devices request the wrong filename, if the LMN dhcp server is used.
In the end - for devices with PXE flag 3 (and 2?) in devices.csv and "Systemtype = efi64" in start.conf filename "linux/pxelinux.cfg/elilo.efi" should be set in /etc/dhcp/devices.conf