ADFS Sign-in page won't load custom font - customization

Question

I am customizing my ADFS 3.0 sign-in page and I have created a custom theme and modified the stylesheet to add a new font family (FontAwesome). Here is the font definition in the stylesheet.
#font-face {
font-family: 'FontAwesome';
src: url('./fontawesome-webfont.eot?v=4.6.3');
src: url('./fontawesome-webfont.eot?#iefix&v=4.6.3') format('embedded-opentype'), url('./fontawesome-webfont.woff2?v=4.6.3') format('woff2'), url('./fontawesome-webfont.woff?v=4.6.3') format('woff'), url('./fontawesome-webfont.ttf?v=4.6.3') format('truetype'), url('./fontawesome-webfont.svg?v=4.6.3#fontawesomeregular') format('svg');
font-weight: normal;
font-style: normal;
}
I executed the following Powershell commands to add the additional resource files to ADFS (I even tried to add the ?v=4.6.3 to the Uri but still got the same errors ):
Set-AdfsWebTheme -TargetName CustomerPortal -AdditionalFileResource #{Uri="/adfs/portal/css/fontawesome-webfont.woff";path="C:\ADFS_CustomerPortal_Theme\css\fontawesome-webfont.woff"}
Set-AdfsWebTheme -TargetName CustomerPortal -AdditionalFileResource #{Uri="/adfs/portal/css/fontawesome-webfont.woff2";path="C:\ADFS_CustomerPortal_Theme\css\fontawesome-webfont.woff2"}
Set-AdfsWebTheme -TargetName CustomerPortal -AdditionalFileResource #{Uri="/adfs/portal/css/fontawesome-webfont.ttf";path="C:\ADFS_CustomerPortal_Theme\css\fontawesome-webfont.ttf"}
Set-AdfsWebTheme -TargetName CustomerPortal -AdditionalFileResource #{Uri="/adfs/portal/css/fontawesome-webfont.eot";path="C:\ADFS_CustomerPortal_Theme\css\fontawesome-webfont.eot"}
Set-AdfsWebTheme -TargetName CustomerPortal -AdditionalFileResource #{Uri="/adfs/portal/css/fontawesome-webfont.svg";path="C:\ADFS_CustomerPortal_Theme\css\fontawesome-webfont.svg"}
Set-AdfsWebTheme -TargetName CustomerPortal -AdditionalFileResource #{Uri="/adfs/portal/css/fontawesome.otf";path="C:\ADFS_CustomerPortal_Theme\css\fontawesome.otf"}
When I refresh my sign-in page I get the following errors in the console.

Answer 1

I was having the same issue and found that ADFS's custom themes cannot actually serve font files: there's nothing in the documentation on this, but Microsoft confirmed that in the answer to this question.
They do suggest a workaround, where you use a .css extension for the URI but actually use your font file as the path:
Set-AdfsWebTheme -TargetName Custom -AdditionalFileResource #{Uri="/adfs/portal/vegan.css";Path="C:\webtheme\css\Vegan.ttf"}