When the first option in a font stack is missing, WebKitGTK uses the default Sans alias instead of trying to match the next option.
E.g. on GitHub, the font stack for code snippets is "SFMono-Regular, Consolas, Liberation Mono, Menlo, monospace". If you don't have a match for "SFMono-Regular", WebKitGTK uses the default Sans font, instead of trying to match "Consolas", then "Liberation Mono", etc.
When the first option in a font stack is missing, WebKitGTK uses the default Sans alias instead of trying to match the next option.
E.g. on GitHub, the font stack for code snippets is "SFMono-Regular, Consolas, Liberation Mono, Menlo, monospace". If you don't have a match for "SFMono-Regular", WebKitGTK uses the default Sans font, instead of trying to match "Consolas", then "Liberation Mono", etc.