This question mentions that it's an open question whether the Mandelbrot set is path-connected and the answer conflated it with the more famous open question of whether the Mandelbrot set is locally connected. But locally connected and path-connected are different notions and it's not obvious that they are equivalent in this case. Are they equivalent for the Mandelbrot set?
Here's a possible proof for the Mandelbrot set being path-connected: There is a homeomorphism between the complement of the Mandelbrot set and the complement of a closed disk. This homomorphism can be used to define a continuous function from a circle onto the boundary of the Mandelbrot set, which witnesses that the boundary of the Mandelbrot set is path connected. Any set with path-connected boundary has path-connected closure, and the closure of the Mandelbrot set is the Mandelbrot set itself since it is closed. Where does this argumant go wrong?
According to this question any compact metric space that is connected and locally connected is path-connected (according to a comment by John Samples, the proof is long).