My location says: Belgrade, Serbia. If you're interested, you can find it here (zoom out a few clicks to see this part of Europe):
You'll see a large river running from NW to SE through it
I sail on Danube river (mostly), some inland lakes and Adriatic coast of Montenegro in the summer. What is unusual here is that inland sailing is chalenging (sometimes brutal), while the coast is mellower (although it has its share of storms of course). Yes, if you count the light wind days in my area, longboards may make sense, but you also have between 50-100 good days a year (from 11 to 40+ knots). More than enough for me.