I’ve had a 2012 Nexus 7″ for a while now and performance has been dropping off over the last few releases of Android, Lollipop being pretty poor but better than some.
I’ve just flashed the Nexus back to KitKat 4.4 and performance is really good again. There’s a lot of contravening steps out on the Internet but I stuck with the instructions provided by Google which worked out fine.
I was using Ubuntu to control the device and had to download the SDK to get to the compiled tools needed. Hundreds of MB for just a couple of executables. Still, it was a good introduction to udev to allow the Nexus to be recognised as a device.