Maybe check YouTube. Many PF maps already had videos made of them.
If no video exists, and old replays exist on the map page...
You can use the frozen install of ManiaPlanet 3 to watch the replay:
https://forum.maniaplanet.com/viewtopic.php?p=283980#p283980
One of the things that changed between ManiaPlanet 3 and ManiaPlanet 4, in Canyon for instance, is that the car starts with the wheels on the ground, instead of the wheels slightly above the ground. Little changes like this, in addition to updated block geometries which optimized the game, broke most PF maps. I don't think any backwards compatibility will be added for such maps.
For normal race maps, we can update them. For PF maps, it's probably a lost cause. But at least we have replays.