Try disabling DVR-ROM (disconnect it) – this helped me on other platforms.

Update: I added nomodeset to the grub.cfg and I can see more of the kernel output. It tries to read from /dev/sr0, but fails after a large number of attempts. I assume this is the DVD-ROM? Anyway it eventually gives up trying to read from /dev/sr0 after many tries and says it cannot locate a live file system. It then offers to boot from the network. I checked that my PARTUUID was correct for sdb1 (the partition where the Ubuntu live filesystem resides), and it was not. So I fixed PARTUUID after checking it with blkid on another machine, and set it correctly. But it still ends up in the same state, trying to unsuccessfully read from /dev/sr0, then failing to boot the live file system.

I got a little bit further by adding noefi parameter back to grub.cfg. Now I can see kernel messages after the kernel starts to load. It stops at the following line:

fb0: switching to radeondrmfb from EFI VGA

It has been stuck here more than 10 minutes…

I have tried both disk creator in Ubuntu 20.04.1 and the manual method, both seem to end up with the same black screen. I followed the instructions with a few adjustments:

1. I removed the noefi parameter from grub.conf, as per instructions that it’s no longer needed. I have not tried it with the parameter, yet.
2. I used the correct name for initrd in my grub.conf

My Mac has no issues seeing and booting from the EFI usb. I get the grub menu, choose Linux and press enter. Then, I get a black screen with non-flashing cursor for a minute or so, then the screen goes completely blank… then… absolutely nothing seems to be happening. I have left it this way for at least 5 minutes, but nothing happens.

Any ideas? My Mac is fully up-to-date running 10.7.5 Lion, the latest supported OS X version. My plan if I can get a live environment to boot is to then shut it down and swap the current HDD for a spare 256GB SSD that I have lying around, then install pure Ubuntu on the SSD.

I rebooted and dropped to the grub command line. It sees two devices: hd0 with partitions named apple1, apple2 and msdos2, and hd1 with partitions gpt1 and gpt2.

hd1 is the internal disk, and gpt1/ gpt2are presumably /boot and /. Unfortunately, grub returned ‘unknown file system’ when I tried to list the partition files.

Really have no idea what to do next. I’ve tried both methods for creating a USB stick. The manual method simply generated an error that it couldn’t find a live file system and dropped to an initramfs shell.

Thank you for taking time to document you experience and the write up! I am sure you saved many hours for us in the future!

My aim was to create a dual boot mac os lion and ubuntu 20.04 desktop on my Mac Pro 1.1 -> I think I got it working now 🙂

I have ran the install process probably around 10 times now and have struggled with the black screen after the installation of Ubuntu for a couple days and I have booted the os a couple of times but I wasn’t able to boot consistently. What I noticed is that the OS boots after the initial clean install. Either without grub interaction or, when that gives a black screen, with the grub commands:

set prefix=(hd0,gptX)/boot/grub (replacing X with the number to your root partition)
insmod normal
normal

Grub should show up, press “e” to edit the grub entry.
The question I had being quite new to this is that I was not completely sure where to add the “noefi” parameter in the grub entry. I just now figured out it should be placed at the end of the line starting with “linux” in the grub entry. And appending after what is already within “…” in the line GRUB_CMDLINE_LINUX_DEFAULT=”…” in file “/etc/default/grub” Hope this helps newcomers that are stuck at the black screen after installation. Now you should be able to boot into Ubuntu every single time.

The next issue that I faced was with the 7300 GT graphics card. The most recent linux driver for it is the 304.137 driver -> https://www.nvidia.com/Download/index.aspx?lang=en-us

After reading more about this driver:
https://ubuntu-mate.community/t/nvidia-304-driver-install-in-18-04/16787
I realised this video card is not going to work reliably in Ubuntu 20.04. I however had a Nvidia 8600 GTS collecting dust, and after checking with the link above I discovered it uses the 340.108 driver. Worth a shot. However I needed to order and wait for the mini 6 pin cable to arrive that supplies additional power to this card.

During the initial install and when booting up there are massive artefacts on the display but you are able to see just enough to work your way through the install. A trick I discovered that helps is to have two windows open en select the window you are not interested in (for example the file browser) the other “non-active” window will have less artefacts. Janky but I found this to be the only way. I noticed that when I inserted both graphics cards ubuntu would not boot and get stuck during the boot process and restart itself over and over again. So for now just keep the 7300 GT running and boot into Ubuntu (again with a lot of artefacts flying around).
Open terminal and run:

sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update
sudo apt-get install nvidia-340

Now shut down your machine. Take out your 7300GT and insert the new graphics card. In my case the 8600 GTS. Make sure to have Ubuntu selected as default to boot because you will not be able to see the boot screen without the 7300GT or a mac efi flashed or compatible mac card.
Boot the system and after some time you should be greeted with the Ubuntu login screen. Login and there should be no graphics abnormalities.
Hope this helps!

This must be the problem. I just read through the original 14.04/16.04 post and realised I this 18.04 update blogpost stops at installation where the original post still contains steps during installation and after installation which I did not do.
I did not create the EFI partition during the install and I did not mess around with grub after the install. Not entirely sure how to do it as I haven’t messed around with grub much but I’d like to learn more about it so I’ll give it another go tomorrow. I basically got the install usb booted and just went through a normal install process. Any hints or tips that might help me out are much appreciated 🙂

Could you try to manually boot from hard drive?
Essentially, boot from USB, interrupt grub, manually set your hard drive as boot point and continue?
Once booted from your hard drive that way you can then just update grub from command line.