iMac 27 Opencore boot issue after NVRM reset

[thinkingslow]

Hi folk. Newb here.

So, I triple boot this iMac, setup like this:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI ⁨EFI⁩                     209.7 MB   disk0s1
   2:                 Apple_APFS ⁨Container disk1⁩         300.5 GB   disk0s2
   3:           Linux Filesystem ⁨⁩                        199.7 GB   disk0s3
   4:                 Apple_APFS ⁨Container disk2⁩         500.2 GB   disk0s5

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +300.5 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume ⁨Macintosh HD - Data⁩     136.1 GB   disk1s1
   2:                APFS Volume ⁨Preboot⁩                 1.0 GB     disk1s2
   3:                APFS Volume ⁨Recovery⁩                624.5 MB   disk1s3
   4:                APFS Volume ⁨VM⁩                      2.1 GB     disk1s4
   5:                APFS Volume ⁨Macintosh HD⁩            15.3 GB    disk1s5
   6:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.3 GB    disk1s5s1

/dev/disk2 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +500.2 GB   disk2
                                 Physical Store disk0s5
   1:                APFS Volume ⁨Macintosh HD2 - Data⁩    266.1 GB   disk2s1
   2:                APFS Volume ⁨Preboot⁩                 2.2 GB     disk2s2
   3:                APFS Volume ⁨Recovery⁩                1.2 GB     disk2s3
   4:                APFS Volume ⁨Macintosh HD2⁩           13.0 GB    disk2s4
   5:                APFS Volume ⁨VM⁩                      1.1 MB     disk2s6

The first disk runs Ubuntu, the second runs Big Sur natively, and the third runs Somona with OpenCore. But the fan was running a lot on the latter, so I stupidly executed an NVRAM reset. Now, Sonoma won't boot, and just shows a screen showing support.apple.com/startup. The system now boots straight into Ubuntu unless I hold down the Option key, where I do do see options to book EFI (which boots Ubuntu), HD (boots Big Sur), and HD2. I am able to boot Big Sur.

I have spent hours trawling forums trying to fix this, and have found nothing that helps. Remedially, I have tried to bless using recovery from Big Sur, and have also rebuilt OpenCore from Big sur.

I'd be somewhat surprised if another newb hasn't done this before, but I simply can't find the solution. Any help/pointers would be hugely appreciated.

 

[thinkingslow]

And interestingly, using my OpenCore Somona USB booter works.

I can also use the efibootmgr in the Linux install, and it shows this:

BootCurrent: 0000
Timeout: 5 seconds
BootOrder: 0000,0080
Boot0000* ubuntu    HD(1,GPT,ae544b49-ab6c-4644-8e99-c72e0a2ad998,0x28,0x64000)/File(\EFI\ubuntu\shimx64.efi)
Boot0080* Mac OS X    PciRoot(0x0)/Pci(0x1c,0x0)/Pci(0x0,0x0)/Sata(0,0,0)/HD(1,GPT,ae544b49-ab6c-4644-8e99-c72e0a2ad998,0x28,0x64000)
BootFFFF*     PciRoot(0x0)/Pci(0x1c,0x0)/Pci(0x0,0x0)/Sata(0,0,0)/HD(2,GPT,a9a97bbe-b930-4e95-9e52-dec855cbd0e1,0x64028,0x22fa3480)/VenMedia(be74fcf7-0b7c-49f3-9147-01f4042e6842,4fc2c2390207ac42a720607b885e3447)/File(\E50412D9-8EF0-316A-811B-FE422D007BE6\System\Library\CoreServices\boot.efi)

Not being awfully technically minded, but does that hint that the Sonoma boot record is messed up? I'm not sure changing the order would help here, as the Sonoma just won't boot.

I have also tried this, but get a black screen: opencore-uefi-disappers-from-boot-options-after-5cbeea65

 

[thinkingslow]

Right, sorted it. Copied the EFi from USB to Mac EFI, and bada ding.