I'm using Chrome and I can't figure out how to achieve this. Setting 'minimum font size' in settings and choosing 'always use this font' doesn't work as it still seems to depend on the locale/language. I just want things to be readable - use a sans serif font in all websites, with a min font size of say 15px. What extensions can do this?
I would suggest to you to try uBlock Origin and enable option "Block remote fonts". This should block remote fonts from being downloaded.
webfonts are not the problem, they would be sizes also. btw which results you got in chrome store? already tried yourself? https://chrome.google.com/webstore/ stylish could accomplish that but sans-serif is critical and NO official web compatible font like Times/Times New Roman, Helvetica, Georgia, Arial, Verdana - or Open Sans. the first is matter. the rest are fallbacks if not usable. but this breaks in any way websites and its layouts, promised.