The only known exoplanets are in the Milky Way - we can't yet detect them around the vastly more distant stars of other galaxies, except perhaps in the rarest of circumtances.
Several of the methods used for finding exoplanets are biased so that they're more likely to find exoplanets that are both really big (Jupiter-size or bigger) and really close to their star (much closer than Earth)
As methods of detecting exoplanets get better, I think they're starting to find more systems with multiple planets so the average is probably more than 1
Not an astronomer but if I'm not mistaken, we find exoplanets based on the shadows from their respective stars, we can usually tell if a star has multiple planets orbiting based on the amount of light we see, it's just that it's strangely more common to only have 1 planet orbiting each star, instead of the many we have.
If you zoom out to about 100,000 light-years and rotate to above the ecliptic of the galaxy, then the software displays the rest of the stars in the galaxy also. A cool perspective on the data.
