Ran into another problem, having to do with the color profile for the display. Background, at one point I was doing color management professionally, profiling displays and printers, so I have the equipment to create custom profiles. Preview and Photos both work with the "unsupported monitor" default profile, but since I have a wide gamut display all images come thru overly saturated. I installed the custom profile using Displays, Colorsync was happy with it, all sections legal. However, once installed, anytime I click on an image in Photos it ab ends immediately, producing a large report. Preview works fine with my custom profile, rendering a test image correctly (a printer reference image with ProPhoto as the embedded profile).
The display is a BenQ SW2700PT, so I went to their site looking for any Mac related software/drivers, but nothing useful. The "unsupported monitor" default profile is a standard icc format, as is my custom profile, but for some reason Photos plays okay with it but not with mine. Like Maps, not a big loss, if I get serious about any image editing/displaying/printing I'll load up Gimp or something similar. Used Photoshop since the beginning of time, but not much lately, so I cancelled my subscription.
I assume the problem is similar to GPUs, no way to tell the guest what type of display from the host?