Hello,I'm A Russian and my hobby is learning languages.I have relatives from Sakha but they're Russian.Sakha is an endangered language and I want to learn it so if Duolingo could take into consideration adding Sakha then I'd appreciate it.
With 450 000 native speakers I wouldn't consider it to be endangered.
I doubt that Duolingo will ever add this language, but you can never know. Meanwhile I would learning it on Memrise instead
They've added languages a whole lot "smaller" than this one. Granted, it might be more feasible in many ways as a course for Russian speakers, which would probably make it quite underappreciated by the folks in Pittsburgh. Russian-language Duolingo is in my opinion the most vibrant corner after English of the ones I'm familiar with.