Firstly, take the seat and cover off. Now try to imagine it without fillets. It’s all blended together to make it look like one thing, but the geometric shapes should call out at you.
The part the sits against the wall can be made from an extruded outline. It’s just 6 points to get the shape, and it looks like it has a radius on the bottom. Then it can be extruded.
There is a an area where the seat went, the top is just a rectangle that’s radiused on one end. That can be extruded down.
There’s a mere rectangular box that comes from the wall plate, near the floor.
There’s a truncated cone that supports the bowl.
The bowl can be made from a sphere that’s been split in half. Now comes the tricky part because they are coplanar and the fillets run out to nothing. The bowl and the the top plate that supports the seat, will have to be matched, perhaps, using the match surface, with added splits. This fillet will be a challenge to get done. Alternatively, you may need to use Rhino’s blend or connect to make the front surfaces coplanar.
A simple box may be subtracted from the top to form the step-like area that the seat…sits on.