Debian 11 build 39 add overlay

I’m trying to follow the instructions: https://wiki.radxa.com/Rock5/guide/radxa-debian, but build number 39 is missing the files: /boot/config.txt; update_extlinux.sh.
There is a need to add a PWM output.
In the build rock-5b-debian-bullseye-xfce4-arm64-20221031-1558-gpt.img, following the instructions, it was possible to add PWM support.