Change the font used in the Breeze SDDM theme

The default Breeze theme for SDDM on KDE uses default fonts from somewhere I don't know of. In earlier versions of KDE/SDDM, there used to be specific files in the SDDM themes where a font could be set (using something like font.family in PlasmaComponents.Label). However, in newer versions (Plasma/sddm-breeze 5.10.1-1, sddm 0.14.0-10 on Fedora 26) everything seems to have been rearranged and I can't find any file(s) where the font can clearly/obviously be set. I would like to change the font for preferably _all_ UI elements. I found this post but couldn't glean much useful information from it. One option in particular, got by following a link in that post, is to just change the system's default (fallback) fonts , and that is something I _definitely_ don't want to do (I need the default fonts as they are for other reasons). I also tried the option mentioned in the original post, by the author of an SDDM theme, of setting the font in the theme.conf file , but to no avail. (To be fair, the author does mention that this technique won't work with other themes. :( ) Is there really a way to change the SDDM font, particularly for the Breeze theme?