Here is an article highlighting the best "all-in-one" maps for a seamless experience. Top OMSI 2 Maps: No External Downloads Required
Maps like Grundorf modifications usually only require the assets already found in your Steam installation. omsi 2 maps ohne zusatz downloads
(v3 Updated) : Known for its high-quality scenery and diverse driving tasks, it is a staple for players seeking a "pure" freeware experience. Here is an article highlighting the best "all-in-one"