Yes, I came to playing by learning to read the dots, then had to struggle to play by ear. Everyone sings 'by ear' first.

I think some of the tips to playing by ear ~(identify the key note) also help with sight singing. But mostly I'm hammering the notes in one by one on the keyboard, then trying to join in Youtube.
But our Mozart is in 8 parts which seem to get divided between lines randomly so the 'alto2' is useless, and the full recording far too fast.