Is there any way to install Ubuntu 20.04 on iMac 5.1 late 2006?

I’ve been trying to revive an old imac for a few days now, there are a few articles describing how to install 64-bit Ubuntu on a 32bit EFI system. I was able to make bootable USB installer stick based on this article. There were a few tries of installing, the cleanest install was with preinstalling grub-efi-ia32 package. The installation went without any errors and I was able to boot to grub without any external drives. At this moment I’m stuck and not sure where to go next. After grub tries to load Ubuntu my imac is stuck on black screen, I also tried nomodeset option which helped me to load from my USB drive, but it didn’t help me with booting to my install.
I don’t need to dual-boot, I just want to run Ubuntu.
Also I did use lvm when installing, although I’m having doubts that it should be used in this particular setup.
Any advises or help is appreciated.

update: after some tinkering with chroot and installing openssh server on my machine I was able to ssh into my system. Basically everything is working except xorg, apparently my videocard is missing its ROM/Driver, although xorg man page tells that my gpu(RV530/x1600) is supported.

My X log have this records:

[KMS] drm report modesetting isn't supported.

And my kernel log:

[drm:radeon_get_bios [radeon]] *ERROR* Unable to locate a BIOS ROM

Still need help, reading a lot of forums and articles couldn’t help me solving this.