Part of cultural history and insight into their daily lives might be lost, but one of the things LLMs should be good at is preserving and enabling the teaching of the language to anyone who may find they need to speak it at a later date.

I'm surprised Ubykh wasn't better documented or recorded since 1992 is fairly recent for a language to die out.

Linguists had been intensively studying Ubykh for decades by the time the last speaker died. It's rather well-documented for a language with few speakers.