Brilliant. That means that
mjpg_streamer is running and seems to be happy. I'm guessing that you're seeing two images, one a snapshot and one a video. The second one is something like http://octopi.local:8080/?action=stream . Just the
/ path from before by itself is some HTML which includes both outputs.
You might want to visit your
OctoPrint -> Settings -> Webcam & Timelapse and see if that's been changed from the default.
If you're trying to reach your OctoPrint instance using HTTPS then it's possible that it doesn't like trying to include an HTTP stream as part of that for the webcam. In other words, just try http://octopi.local/ rather than https://octopi.local/ .