You can get more tracks to appear if you change Netflix UI language in settings, as described here in 2015 by Netflix CPO: https://www.quora.com/Why-arent-all-subtitles-available-in-a...
This is also mentioned in various Netflix help pages, like here, which says 5-7 subtitle languages are shown by default, and you need to change UI language to see the rest: https://help.netflix.com/en/node/13245