Would really like to do a Danube River cruise but my husband uses a walker and can not walk long distances. Most shore excursions seem to be walking, hiking or biking.
European river cruises are a challenge for mobility limited passengers.
Everyone has different limitations but here is a good article that was written for wheelchair/scooter users but has some insight on river cruises.
https://spintheglobe.net/dir/2019/08/04/river-cruises-wheelchair-users/