It seems when we embed google font from acp it works. But if we use google font in our style file it does not work well.
The weird thing I experienced is when I changed my font setting in phpstorm to "Ubuntu" and then I pushed my changes in git using built in plug-in in phpstorm and later udpated my live file, I found that my font-family was overwritten in body, h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6
The setting @julian describes belongs to the browser (chrome/chromium in this case), not NodeBB.
If you're using chrome/chromium, press F12, then F1 to show the options. Check the option and keep the tools open while refreshing the page to ensure the cache is disabled.