I’ve done a little self-help with the online info and Google but haven’t come up with the answer:
Should I expect the SD card slot to work on a minirouter with CM4 that has onboard eMMC?
I’ve got a couple of units and tried a couple of known good SD cards with the onboard reader and no luck with Raspbian or Ubuntu running. Using an external USB reader the cards work.
What I was trying to do: Boot up the device with the SD card to write an OS image to eMMC so I don’t have to open up the case every time I want to re-image. Is this a non-starter?