I'm very interested in using this plugin, and noticed a fairly critical seeming issue on the Github page here stating an issue with Grav's caching.
There seems to be an issue when using Grav's page caching.
When enabled the {{ isMobile() }} and {{ isTablet() }} vars only work intermittently on mobiles/tablets and even intermittently gives a false positive resulting in mobile style sheets etc being loaded for desktop browsers.
I haven't had a chance to play with the plugin yet, but couldn't one conceivably just use one of the other functions as a surrogate, or do they all have issues due to Grav's caching, for those of you who have tried it out? For example, you could potentially use
{{ mobile_detect() }} which returns tablet, phone or desktop
Look forward to hearing your thoughts!