CM3 with eMMC boot from SD (RPI CM4 IO board)

I have used rkdeveloptool on Mac to flash radxa-cm3-io-debian-bullseye-xfce4-arm64-20220801-0218-gpt.img to the CM3.

I can get that to boot, but it would be easier for me to use SD to boot. Is that possible?

The instructions at are a bit messed up.

It says to “Write the image to microSD card” and then the next step is to “Erase microSD” which makes no sense to me.

Then “Part three: Write U-Boot images to microSD” is also confusing. It says, “We have prebuilt u-boot images built via rockchip-bsp SDK. They’re idbloader.img and u-boot.itb.”

But it doesn’t say where to find idbloader.img and u-boot.itb for the CM3. Are they available somewhere?