You can definitely surf in Munich in the middle of the big big park. But it’s really just a manmade little waterfall that guys “surf” on, but you don’t go anywhere, just ride the waves in one place.

There is a video of this on the Germany page, have a look… I bet the guy that posted it could tell you where to go.

As you’ve already read there is river surfing in Munich, Germany. I heard they even hold a competition for it each year.
There are other rivers in the world that people can river surf on: including the amazon, and rivers in costa rica and new zealand.
The only other river in Europe that would create “the waves” is the river severn in England. This is due to the clash of the river meeting the tidal currents from the ocean (also why areas of the amazon are perfect – - if your not afraid to go in the water). However i don’t know if river surfing is allowed in England…