At least on a percentage basis, the Steam Linux marketshare grew slightly for January 2018.
The monthly statistics are out from Valve and the Steam Survey shows the Steam Linux marketshare for the month at 0.41%, or an increase of +0.15%. It’s quite an increase for Linux but for January macOS reported a 0.42% increase (1.84% overall) while Windows still dominates with a 97.76% marketshare.