PWM export: Device or resource busy

I’m trying to get PWM up and running on my Beaglebone Black following the example of beagleboneblack - PWM on BeagleBone Black (v4.14) - Stack Overflow
beagleboneblack - PWM chip to pin mapping on BeagleBone Black (v4.14) - Stack Overflow

When I try to export 0 > /sys/class/pwm/pwmchip0/export or any other pwmchip, I get
-bash: echo: write error: Device or resource busy . What am I doing wrong?

I don’t have an SD card so can’t flash the latest image, but my board is running Debian 10. If there’s a way to check exactly which image, I’ll be happy to check that.

Execute in a terminal

uname -a

You may be interested in checking further PWM examples

uname -a
Linux beaglebone 4.19.94-ti-r42 #1buster SMP PREEMPT Tue Mar 31 19:38:29 UTC 2020 armv7l GNU/Linux

Right now, I’m hoping to use PWM through the Linux filesystem. It doesn’t look like either of those examples apply.