There are many endangered languages, most of them are old languages or specific dialects from the middle of bumfuck nowhere, tribal languages and the like, and the newer generations either moved out to civilization or otherwise speak their country's normal languages because of schools.
Many are African or Native as there's hundereds of different old tribes around the world and almost none of them write.
According to Babbel, Khanty, a Western Siberian language with three dialects, is probably one of the most endgangered language with an actual chance to be restored, with less than 10,000 people who speak it, it's dying out but there's still enough people who speak it to be revived.
I'll give a mention to Cornish as a really obscurely spoken language. It's a community language from Cornwall, Britain. It is essentially a dialect of Welsh but is seperate enough to be recognized as its own language. There's about 300 people who speak it fluently but it is undergoing a revival. Cornish is interesting in the fact that it was basically extinct at some point. While realistically it's not a language that will be solely spoken in an area because everyone speaks English, it *is* in a more civilized part of the world (insert British joke here) so it's more practical to revive it for history and culture's sake.
The languages with a few dozen people who speak them in a remote tribe are pretty much dead unless there's a REALLY dedicated researcher who tries their best to get it down to writing. There's some African tribal languages with like 10 people who speak it fluently. But then you have languages like Njerep which has only 6 people who can only speak a few phrases. It's dead in all but name.
I hope this answer piques your curiosity a bit.