They give you the option to choose between like four, maybe five languages. That's it!
If you want subtitles in any of the other hundred or so languages that they have available, well... no. Just no. Learn one of the four they've picked for you.
If you call their support, they'll gaslight you and mumble something about "copyright", which is patent nonsense. Copyright doesn't restrict Netflix from showing more translations for their own content that they made themselves. They own the copyright on it, which means, literally, that they have the right to do whatever they please with the copy. Including showing the associated subtitles to you.
You see, what actually happened, is that some too-smart UX guy at Netflix couldn't make a language picker look nice for that many options so he asked a too-smart data science (lol) guy to figure out the most common languages for each region.
Here in Australia they picked English, Italian, Vietnamese, Chinese because we have a lot of immigrants from those countries. I'm sure they used very clever algorithms on big data clusters to figure that out. Good job, well done.
Never mind that every other streaming app vendor figured this out. Netflix and their $500K total comp Stanford or wherever graduates couldn't. So they instructed their call centre staff to lie to their customers.
Then they had someone write this idiocy: https://help.netflix.com/en/node/101798
"If subtitles for a title are offered in a language but do not display on your device, try another device."
Oh, oh, I'll go do that right now! Let me try my PC... nope four languages. On the TV? Four languages. Actually, I have a phone... and... oh... four languages.
PS: Thai (only!) subtitles are "special" and use eye-searing HDR maximum white. Like 1,600 nits white that literally leaves green after-images etched into my retina. They have a support page and a pre-prepared set of lies for the support staff to read for that piece of shoddy engineering also.