Bug#1140659: powerdevil: Lacks permissions to access I2C devices

Hi,

I had the same issue (Debian testing with KDE Plasma). 

I found a workaround after reading those links :

https://discuss.cachyos.org/t/powerdevil-related-errors-when-trying-to-access-i2c-error-eacces-13/10233

and

https://wiki.archlinux.org/title/Udev#Allowing_regular_users_to_use_devices (see note)

Create this file to override existing udev rule(*):

sudoedit /etc/udev/rules.d/69-i2c-permissions.rules

with this content:

SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", MODE="0660", GROUP="i2c", TAG+="uaccess"


(*) /usr/lib/udev/rules.d/60-i2c-tools.rules provided by i2c-tools package

--
Bruno