It's an interesting idea to patch the holes when absolutely no srt files are available.
But why not have an open repository where already present srt files could be shared by people.
We could call it libre-subs or something like that.
Facebook is, as far as I can tell, a lot more user-centric which might lead to a 'Everything is about you' mentality. So commenters over there might be more prone to think that whatever they have to say is relevant and could add value. While lemmy-likes are a lot more content focused, not even highlighting the user name of authors a lot. So comments have to be able to exist on their own without a 'face' connected to it.
Not sure if this makes sense.
I was only aware of the m.2 variants.
Still, it's a thing to be bought which I have not had to do for years for my media solution.