Creating custom maps using a map.dat file (for 1.18.2, Fabric) doesn't work. They just don't render at all. It is something to do with the Immersive Portals mod because these maps work on vanilla 1.18 ...
I have earmarked each step (as significant) with chat messages. These will be parenthetical. I figured you could use something to CTRL+F at each step. I cannot confirm that this issue has not already ...