Now I have Ubuntu 18.10 installed.
Workaround is to use a working grub2 (for example booting up with Ubuntu 18.04 installation media) and move to grub command line. There I created a new menuentry for loading Ubuntu 18.10 installer from another USB stick.
https://askubuntu.com/questions/436519/boot-efi-files-from-grub2
Now I have Ubuntu 18.10 installed.
Workaround is to use a working grub2 (for example booting up with Ubuntu 18.04 installation media) and move to grub command line. There I created a new menuentry for loading Ubuntu 18.10 installer from another USB stick.
https:/ /askubuntu. com/questions/ 436519/ boot-efi- files-from- grub2