If you're using 2.4.x for Linux, I've found a work-around. Download and install Courier Screenplay (available on Fade In Pro's website). Then put these names in the Name Slot... DO NOT put anything in the File slot below — if you do Trelby will not print to PDF. Also, don't add the .ttf extension. Just the name of the font. As in...
Normal: CourierScreenplay
Bold: CourierScreenplay-Bold
Italic: CourierScreenplay-Italic
BoldItalic: CourierScreenplay-BoldItalic
Trelby 2.4 now works as it used to for me. Unfortunately it does not allow you to save Script Configuration files with the sconf extension. Trelby will, however, load them in. So if you already have an sconf file you can copy it to your .trelby (with a dot) folder and load it in Trelby — (I have one called LetterBold that uses Letter instead of A4 and Bolds the Headers, Shots and Transitions in both the Display Screen and in the PDF output. I've attached this sconf file if anyone wants it. I just load it in with each new document, then save the document and I don't have to make all the changes by hand. You can edit this file to taste with a text editor. This .sconf file has the Courier Screenplay fonts installed. To use it you'll need to download and install the Courier Screenplay font — available here...
https://www.fadeinpro.com/page.pl?content=downloadScroll down to the EXTRAS section and then look under fonts.
Apparently I can't attach a file? If anyone wants the file send a private email, I guess.