Added December 27, 2018.
Taken from https://en.wikipedia.org/wiki/List_of_nonlinear_partial_differential_equations
Klein Gordon (nonlinear). Solve for \(u(x,y)\) \[ u_{xx}+u_{yy}+ \lambda u^p=0 \]
Mathematica ✗
ClearAll["Global`*"]; pde = Laplacian[u[x, y], {x, y}] + lambda*u[x, y]^p == 0; sol = AbsoluteTiming[TimeConstrained[DSolve[pde, u[x, y], {x, y}], 60*10]];
Failed
Maple ✗
restart; pde := diff(u(x,y),x$2)+diff(u(x,y),y$2)+lambda*u(x,y)^p=0; cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,u(x,y),'build')),output='realtime'));
sol=()
____________________________________________________________________________________