Just reading this morning...if you want ripe bananas cover a cookie sheet with foil...lay bananas on foil and set oven to 350* for 15-20 minutes.
It was a video and the resulting bananas looked black but were soft inside.....they were using them for banana bread so they looked mushy so, if you try this, I would recommend you wait just 5-10 mins.
Here's the video.
https://www.youtube.com/watch?v=xaAbkvZ5Ivs