My default accommodation on tour is camping. Campgrounds in Europe tend to be much nicer. Many Europeans travel to a campground and settle in for a month of vacation. Campgrounds will often have a common building, and an actual kitchen (more true in the cooler climes).
Many long-haul cyclists choose wild camping; finding a quiet place somewhere off the side of the road.
While rare in the US, hostels are plentiful in Europe. Hostels can best be summed up as shared living space, with multiple people in the same room, often on bunk beds.
B&Bs (and AirBnb)
A significantly more expensive way to travel.
If you’ve worked your way down to here, you’ve found something more expensive than B&Bs.