I run Mystara, but I don't stick to the Known World and have played a bit loosely with canon. I placed the Thunder Rift between Glantri and Wendar, have thrown in the Icewind Dale on Skothar (I needed a quick mini-campaign so I stole the Icewind Dale 2 story) and I threw in Freeport off the Serpent Peninsula (I needed another mini campaign and that was a place to start).

I briefly ran an L5R game with some fairly radical changes to canon. Most of this was de-retconning some official things, some of it was getting rid of official nonsense without replacement. and a little was my own addition. These changes wouldn't really impact play in any meaningful way but they made me happier.

We played Dragonlance for many years, where the War of the Lance never happened.