Forget the auto ferry. Forget the K-D cruise boats.
You posted the Bingen-Rüdesheimer passenger ferry link in the original post. The Bingen-Rüdesheimer company operates the ferries that connect Bingen and Rüdesheim. There have traditionally been TWO B-R ferries:
- a foot-passenger-only ferry that is close in by the cruise boat docks
- an auto ferry that also accepts foot passengers, which is further upstream and far from everything else
The B-R site says that their foot-passenger-only ferry is not running. However, B-R also has multiple day cruise boats for different types of cruises which dock in Bingen and Rüdesheim. So for foot passengers like you who want to cross from Bingen to R'heim and back, B-R is offering their day cruise boats. You pay the same fare you would for the ferry crossing, but you board one of the B-R day cruise boats instead. The day cruise boats which are available to take you across and back are on the B-R passenger ferry schedule... Click on the link provided in your original post. Then click on Fahrplan 2024 just below the calendar and clock symbols. The pop-up timetable shows an "ab Bingen" column (from Bingen) and an "ab Rüdesheim" column (from Rüdesheim.) The times you see there are the times when the day cruise boats will dock to pick up passengers on the Bingen waterfront (Brücke 4-5)
The auto ferry positioned further upstream has its own schedule on a different page...
https://www.bingen-ruedesheimer.de/rheinfaehren/autofaehre/
Click on Fahrplan 2024 at this page if that distant crossing point matters.
Bingen-Rüdesheimer