I am trying to reproduce johnd2's method.
During booting of the router I see regular U-Boot and kernel messages on my UART console.
But I can't type anything or get the boot process to halt, so it is not clear to me what the step "Start recovery/debrick procedure" means.

I have a BR01 (international) model from 11/2021 with fw 1.0.35 and according to routers fac_info page uart, telnet and ssh are disabled.