Right, what I said above
Quote
Now you already have OpenWrt on NAND, you can go one step further and set up the envs to dual boot Debian on USB and OpenWrt on flash.
So now what u-boot had you install? is that OpenWrt u-boot? you current envs are for booting Debian only. So you have erased the bootcmd for OpenWrt.
Please do this: with the Debian USB rootfs attached, power up, and let it boot all the way into Debian login prompt.
And post the entire serial console log from the u-boot banner (it's important to see everything).
-bodhi
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