See also Where to put custom CSS file.. | NodeBB.
Another possibility is a custom css file overriding the others by having the last <link rel="stylesheet" href="..." /> line in the theme source.
is there a way to completely bypass NodeBB's favicon system? Meaning, a way to use a set of favicons instead of going in the admin panel and adding it under Settings->General?
The reason I'm asking this is because the admin panel only allows loading one favicon size, which works fine on PC browsers but turns out terribly in many other devices that require other sizes.
So this actually requires some manual work, but basically make sure no custom favicon is set in the admin panel.
Then go to your NodeBB installation directory and replace the
favicon.ico in the
public folder with your own custom one and restart NodeBB. I did this a while back for the same reason you mentioned, one small issue to keep in mind it will still only be one size (16x16) when logged in due to the favicon image processor that adds a notification count to it and adds it directly to the
<head> html tag encoded as base64.
But at least it will change the default for not logged in users and whatever else directly looks at http://example.com/favicon.ico, you can check it out on my site here.
Have you tried to include multiple resolutions in your icon? I have used an online ICO converter (https://www.icoconverter.com) and I was quite happy with the result.