Here is a different (in my opinion probably better) source: https://analytics.usa.gov/

It also shows Linux above 5%. I agree that most people are switching to phone and/or tablet, but: the total devices are increasing AND the total number of phone/tablet devices are increasing AND the linux share is increasing

I would expect that as the denominator (all devices which includes an ever increasing number of phone/tablet) increases that Windows, mac and linux would decrease. I am surprised (and happy) that Linux is increasing!