install/53574: UEFI installer not working past 1st menu on iMac 7,1

[dario%darioniedermann.it@localhost]

>Number:         53574
>Category:       install
>Synopsis:       UEFI installer not working past 1st menu on iMac 7,1
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Sep 05 16:10:00 +0000 2018
>Originator:     Dario Niedermann
>Release:        8.0
>Organization:
>Environment:
>Description:
Trying to install NetBSD-8.0/amd64 onto an iMac 7,1* (mid-2007, Intel Core 2 Duo, 1GB RAM) using the 'NetBSD-8.0-amd64-uefi-install.img.gz' image, uncompressed and dumped to an USB stick.

The USB stick is seen by Apple's boot manager (option key held down at start), and it boots up to a point.

It gets to the first 4-option menu, shown in small grey type within a square area in the middle of the screen. From here, if I select:

(1) numbers are printed and the cursor flickers for a while, then the area is cleared and the underline cursor goes to the area's top left. After this, the screen flickers briefly: white, then black. I get a small white block cursor at the top left of the black screen, then nothing;

(2) to disable ACPI: numbers, flickering cursor; the area is cleared and the grey underline cursor goes to the area's top left; then nothing;

(3) to disable ACPI and SMP: same thing as (2)

(4) I get the boot prompt. I try 'boot -c' and I get the same thing as (2).

So far, I have found no way to go further.


*full specs for the exact model: <https://everymac.com/systems/apple/imac/specs/imac-core-2-duo-2.4-20-inch-aluminum-specs.html>

>How-To-Repeat:

>Fix: