Examples of websites using
Plain
('Plain' is a sans-serif font designed by François Rappo and released by Optimo in 2013. The family consists of 11 individual styles, including regular, italic, and bold weights)
with
Silk Serif
(Silk Serif is a serif font designed by Rakel Tómasdóttir and released by SilkType in 2017. The font family includes multiple styles and weights)