Diffusion coupled with boundary equation (mixed-dimensional)

variational formulation
2

I have since updated to the latest Docker container (built 15-04-2021). The MWE now throws the following error:

fenics@9b3d9606959f:~/shared$ python3 MWE.py 
[problem] create list of residual forms OK
[problem] create list of jacobian forms OK, J_list size =  4
[MixedNonlinearVariationalProblem]::check_forms - To be implemented
Solving mixed nonlinear variational problem.
  Newton iteration 0: r (abs) = 9.501e+01 (tol = 1.000e-10) r (rel) = 1.000e+00 (tol = 1.000e-09)
Traceback (most recent call last):
  File "MWE.py", line 80, in <module>
    solver.solve()
RuntimeError: 

*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. ...
*** -------------------------------------------------------------------------
*** Error:   Unable to successfully call PETSc function 'KSPSolve'.
*** Reason:  PETSc error code is: 56 (No support for this operation for this object type).
*** Where:   This error was encountered inside /tmp/dolfin/dolfin/la/PETScKrylovSolver.cpp.
*** Process: 0
*** 
*** DOLFIN version: 2019.2.0.dev0
*** Git changeset:  53a31ce2dc704214325c989d7dfc75b5e9a9d111
*** -------------------------------------------------------------------------