Solving Steklov problem for the bilaplacian

I was wondering if it is possible to solve the following problem in FreeFEM
Screenshot from 2021-02-10 14-28-14
in the space
Screenshot from 2021-02-10 14-29-22

The variational formulation is
Screenshot from 2021-02-10 14-28-22

I tried using Morley elements to try and solve this in 2D, but I get an error when imposing the Dirichlet boundary conditions on u only. It says that all elements of the vectorial finite element should be in the Dirichlet boundary condition.

Is there a way of solving the above problem in FreeFEM ? Thank you for your advice.