The studio's type has Latin, Greek and Cyrillic letters, and Japanese editions add Japanese type with kana and kanji. Words in another writing system, such as Arabic or Hebrew, would print in another type or as empty boxes.
In print: when a manuscript is read, the book's page lists the writing systems in it that the print fonts don't have. Ebooks show them anyway, in the reader's own fonts.
On the cover: as you type, the cover editor checks every character of the cover's words (the title, the author's name, the blurb and the rest) against the characters its type has. It names a writing system it has no letters for ("Arabic letters"), and shows any other character it lacks, such as a heart, an emoji or a rare letter. Covers of Japanese editions are set in Shippori Mincho, which has Japanese and Latin letters but no Greek or Cyrillic ones.