Very common in Europe.

There is a steel frame behind the wall bolted to the wall and to the floor with the water container/chamber, and the toilet is held up by huge metal bolts.

The ceramic toilet part can usually hold minimum 300-400 kg, so you could dance on it without any issue.

It can be fully serviced through the push button plate.

Advantages: visually more clean, easier cleaning under the bowl, quiet operation behind the wall while filling up the chamber with water.