Fails during boot - hangs in 'DRAM' - after attempt to update uboot

The device 6UL SBC fails during boot - hangs after DRAM after attempt to update bootloader

Device (kinda) boots and prints the following:

CPU: Freescale i.MX6UL rev1.1 528 MHz (running at 396 MHz)
CPU: Industrial temperature grade (-40C to 105C) at 47C
Reset cause: POR
I2C: ready

… then it hangs. I mistakenly used the u-boot-dtb-signed-ccimx6ulsbc1GB.imx instead of the u-boot-dtb-signed-ccimx6ulsbc1.imx.
How do I get it back to a proper boot (any hints would be appreciated - I see there are some notes on a serial bootloader, but I’m not sure how that works).

I’ll answer my own question.

There is a perfectly good description on howto recover near-bricked devices at

… so, note2self: RTFM :slight_smile: