These fonts:
https://www.blu-play.com/working.zip
are working on Blu-ray.
Most others aren't.
Can anyone tell me what makes those fonts in the zip special? And how do I change other fonts to do the same?
Maybe BluRay only supports OpenType-Fonts as in your Zip.
No it should support different types.
But I've also tried other OTF files.
There must be some difference between them. And one apparent difference is that other OTF/TTF files contain a lot more glyphs...
But I think there must be more differences.
The only thing that these files have in common is that they have ≤ 256 glyphs. They might be converted Windows 3.1-style TTF files.
OTF is a wrapper for too many types of fonts. It might be helpful to link to a font that doesn't work - but then, there could be many reasons for that too.
I haven't been able to find any other fonts that works.
But if you want one that for sure doesn't work, then try Nunito
Download from anywhere you can find. I've downloaded all versions I could find.
Too many glyphs in that one. Try ASHLEY__.TTF from http://www-ftp.lip6.fr/ftp/pub/pc/garbo/windows/fontstt/ttfonts1.zip - it's ancient
Whatever you're using, it must have a really limited (or very buggy) font renderer