Greasy Fork is available in English.
https://greasyfork.org/en/scripts/466065-blur-on-inactivity with additional features
An extended version of https://greasyfork.org/en/scripts/466065-blur-on-inactivity but with more features (that I wanted)
Default time for the blur to kick in is 30 seconds. If you wish to change that edit the 'inactivityThresholdSeconds' variable in the script (NOT 'inactivityThresholMiliseconds')
Blur intensity can also be adjusted by changing variable 'blurIntensity' to some value between 0 and 100
