I don’t know which one HK65 is referring to, but I know a few examples:

• Punjabi, which is left-to-right in India and right-to-left in Pakistan (the Indian one being influenced by older Indian scripts and the Pakistani one by Arabic)
• Kazakh uses the RtL Arabic script in the part of China where there are a lot of Kazakhs and the LtR Cyrillic script in Kazakhstan
• At least some of the kinds of Tamazight (spoken by Amazigh people, mostly in Morocco and Algeria) use Arabic script, but there is a script specifically for Tamazight languages called Tifinagh which goes left to right and there’s also some use of the Latin alphabet for these languages