I installed the Oswald font family using Skyfonts. I can use it e.g. from LibreOffice. But it does not appear in Scribus. Why?
Scribus needs a line in the font configuration file (Fontconfic) for each separate font storage folder.
Font hiring services make crypted and hidden storage folders into your system. The fonts are taken into use via special server program that tweaks the system to make the hired fonts visible for those programs who ask them in system's way.
Scribus has its own way that bypasses the system and that makes it incompatible.