Hey everyone. I have found a way to fix the issue of receiving Random Maps from other players and then being unable to host them. I have created a Workshop Mod which creates a sym link to your rm2 folder from the mod folder tricking the game into thinking every map is also a mod. This causes maps that are downloaded to now appear in your map list allowing you to host them yourself where previously they would not appear at all.
You can get the workshop item here:
https://steamcommunity.com/sharedfiles/filedetails/?id=1644360846
Let me know if this fixes things and and issues you get. I have set up the .bat command to use relative paths so it should not matter where your game is installed providing you don't move the .bat file before running.