Can't install grub loader error

I am installing LinuxCNC 2.8.0 Debian 10 Buster PREEMPT-RT ISO from a dvd. I keep getting error wont install grub loader.
Do I need internet hooked up to install?

I have sucure boot disabilabled and I could not find where to turn off uefi.

My bios seems real flaky I keep lockup not letting me enter it till I pull the battery to reset it I am going to buy something different.

Thank you

Hello.
Also getting grub install error.
I cant disable UEFI, got one of that new boards. I have tried several ways, but cant, really.
But I noticed in log screen, saying error because package grub-efi-amd64 cant be found, selftrying other package, also missing, so giving it up with error message.
Any idea?

AMD64 system, installing from USB stick, clean install on entire disk, active EFI partition created (520MB), completely offline (maybe this is the error?)

 

There is no problem with "secure boot" (disabled). Another distro installed grub normally. For example, Wheezy have no problem with installing (but have problem with booting because of UEFI, which cant be disabled)

An ideal way for me is somehow install Wheezy with UEFI grub. Wheezy because of RTAI kernel, and EFI grub because damn new board.