I just found out how to fix #hyphenation not working in #Scribus on #Fedora (probably for #languages that aren’t system language):
Check that the text frame (Windows > Content Properties), character and paragraph styles (Edit > Styles, maybe you need to double click on a style to edit) are all the correct language (in my case German on an English system).
If Extras > Hyphenate Text still isn’t working, go to Windows > Resources > Hyphenation Dictionaries and check that you have the correct .dics installed (for me it was only English) and download the appropriate ones if necessary. You can also see the path where they are installed on the system here, so you could manually move a .dic there if you manage to find one.
Tadaa 🎉