Most of the fonts that come with ubuntu are meant for the screen, not for printing, so it's not surprising you are having trouble finding a font proof sheet generator.
Having said that, and surveying tools in ubuntu, here's what I've found. None of these are a complete solution.
font-manager
font-manager is designed specifically for "desktop fonts" and has no print function. However, it allows easy browsing of fonts and can generate decent on screen single font proof sheets in multiple different formats and even has a "compare" mode where you can add multiple fonts one at a time to an on screen proof sheet of sorts.
fontforge
fontforge is meant as a font authoring tool rather than a browser. It expects you to know where the font files are and open them from a file browser. It only does one font per window, but it can print a proof sheet for a single font.
ghostscript
Ghostscript is not a font browser, but a postscript interpreter and previewer. However, it does come with fonts and mechanisms to use them. There are external resources that include postscript font proof sheets, for example https://superuser.com/questions/379384/ghostscript-how-do-i-find-out-what-fonts-are-available
That question shows how to get the list of fonts and hints at ways to render them in a proof sheet.
Anything from this should be viewable on screen or printable. It shouldn't be hard to write something short to generate a sheet using ghostscript/postscript.
