It's not as if YouTube cares much about subtitles
I try to subtitle some of my videos (but it's a tedious process) because southern English accent and slang words means the automatic transcription is sometimes comically bad.. I create srt files in Biftaku Subtitle Editor and upload them to YouTube.
But, wait, via the Studio or YouTube app? No, the app is only useful for setting the description and thumbnail. Google should be utterly shamed by how lousy the YouTube Studio app is.
No, I have to fire up the browser, sign in, go to the studio.youtube.com, get my list of videos, call up the stuff to edit it. Fiddle around because of Chrome's shitty resize-everything-for-some-reason breaking the layout and pushing stuff on-screen. Go to the other pageful of settings, find the bit about captioning. Long-tap to open it in a new tab (if you don't, it'll get claimed by the YouTube app that can't handle the URL). Then, finally, poke around to get to the bit where a dialogue box asks me to pick a file.
What a bloody palaver.