Overview of Heritage Lines in Germany

There is a list in Wikipedia, which is incomplete and sometimes outdated: https://de.wikipedia.org/wiki/Liste_von_Museumsbahnen

Nils started to create a map of the heritage lines and groups in germany, currently Bavaria and Baden-Württemberg are close to finished: https://umap.openstreetmap.de/de/map/museumsbahnen_38011#6/50.785/10.239