Maybe I'm just having a stupid attack, but I can't reset the ui font on a fresh installation of xfe. And the font is a horrible illegible cursive. Lxappearance settings for font are ignored. Edit, preferences, font settings don't seem to have any effect. I can't imagine where this font is coming from. None of my other apps have anything like this.
xfe version 1.42
installed from Ubuntu 18.04 repo
on a plain Openbox system (no DE per se)
I kept trying different fonts in the prefs dialog & while most of them show in the prefs dialog as being reset, restarting xfe had no effect. But I kept trying. And finally found one that worked. So the problem is, either it shows a lot of fonts it shouldn't & when you set it to one of those it falls back to some horrible default of an ornate cursive OR that it should work with those fonts but some reason isn't. So, for anybody with this issue, the work around is KEEP TRYING MORE FONTS. Eventually you'll stumble on one that works. May take you 30 minutes. What I have working now is
normal font: Arial Black [MONO],200,normal,regular
&
Text font: Arial Black [MONO],200,normal,regular.
Not sure which I'm seeing in the UI, but it is legible if not great.
FWIW, an Xresources entry that works for other X applications had no effect.
I still regard this as a bug, but one I can work around.
BTW, something a little more desctiptive than "normal font" and "text font" would not be a bad idea. They're all "text" by definition. I have no clue what the distinction is.
Glad to see you found a workaround.
However, did you try with a fresh xfe config (i.e. do mv ~/.config.xfe ~/.config/xfe.bak and launch xfe)?
In Xfe, the default fonts are 'Sans' for normal font and 'Mono' for text font. These are font generic names and should point to some real font installed in your system. If not, than your system configuration has some problem...
In Xfe, normal font is for the UI and text font (usually a monospace font) is for console messages, editor/viewer, etc.