With Arial:\definefontfamily[mainface][rm][Arial]\setupbodyfont[mainface,10pt]with Optima:\definefontfamily[mainface][rm][Optima]\setupbodyfont[mainface,10pt]It doesn’t matter if the font statements are before or after \starttextThen I thought, let’s test some other things. I logged in as another user, and used ConTeXt from TeX Live 2019:It seems to be that on my system, the standalone installed ConTeXt does not work with Optima, but the TeX Live installed one does.