My fenics version is 2019, I using fenics by docker.

I’m having a problem with non-convergence due to the initial value being too large, so I’d like to know how to set up Newton solver to help my code converge using ‘Newton’s Method with Line Search’.

So there are no code snippets.

You can assign initial data to the unknown function through a projection or interpolation.

If you want a line-search method, I would use the SNES backend of legacy dolfin.