MP 1,1-5,1 Ubuntu 20.04 dual boot, blank screen on 4,1->5,1

[theMotoMan]

I have a 2009, 4,1 flashed to 5,1, running OpenCore from Martin LO. I am using the RX 580.

I can boot from the Ubuntu USB installer and successfully install the OS, but when I reboot afterwards, I never get any video output. If I use my old GT120, everything works well, but if I install the RX 580, the same thing happens.

BTW, right now I am not booting OpenCore first, just straight into the Ubuntu installer. I have OpenCore on another USB stick and when I have it in the first USB port and Ubuntu in the second USB port, it never boots OpenCore first.

Is this a bug in 20.04? Thanks in advance. BTW, I did some searching here and really didn't find anything.

 

[DrEGPU]

Some kind of firmware issue, I think. When grub/bootloader fires up, push "e" to edit the boot parameters. There might be a "quiet flash" or something like that. Replace it with "nomodeset" and see if that fixes. If so, you'll need to find an install the right firmware and drivers for the the RX580. Nomodeset will disable GPU hardware acceleration, I believe.

Editorially, you'd think Ubuntu would've figured this out by now and created a fix!

 

[theMotoMan]

Some kind of firmware issue, I think. When grub/bootloader fires up, push "e" to edit the boot parameters. There might be a "quiet flash" or something like that. Replace it with "nomodeset" and see if that fixes. If so, you'll need to find an install the right firmware and drivers for the the RX580. Nomodeset will disable GPU hardware acceleration, I believe.

Editorially, you'd think Ubuntu would've figured this out by now and created a fix!

So I don't see anything at boot time right now, I am assuming since the RX 580 doesn't support the Mac Boot screen. It seems to be hung before actually booting the OS.

 

[joevt]

Try installing without third party software and drivers. https://forums.macrumors.com/threads/ubuntu-20-04-lts-on-mac-pro-2008-doesnt-boot-solved.2244437/

Or maybe try booting Ubuntu with RefindPlus?

 

[theMotoMan]

Try installing without third party software and drivers. https://forums.macrumors.com/threads/ubuntu-20-04-lts-on-mac-pro-2008-doesnt-boot-solved.2244437/

Or maybe try booting Ubuntu with RefindPlus?

I did see that post and tried without the 3rd party drivers and selected minimal software....no difference. I have not tried Refind, but I did have an older version of Ubuntu booting about a year ago, so something has changed.