Just wondering if you can list some info on filament runout sensor details that will be in 4.1 release so we can prepare for it.
The basic function of these is a switch that is either normally open or normally closed that will change state when the error occurs.
If that is so, can you tell us what GPIO pin you will use, and any other relevant info . That way we can get it all wired up in advance if we want. (and also help you test it in beta versions)