Easy proofs of the undecidability of Wang's tiling problem?

There's a newer proof given in "Two-by-Two Substitution Systems and the Undecidability of the Domino Problem", by Nicolas Ollinger. It seems to be available online at: http://hal.inria.fr/docs/00/26/01/12/PDF/sutica.pdf. Hopefully, it is easier to understand than Robinson's proof.

There is also the newer work of Kari "On the Undecidability of the Tiling Problem", which shows the undecidability of the domino problem by a reduction to the immortality problem for affine functions.

It shows the undecidability of the domino problem in the hyperbolic plane which was not shown by Robinson. I am not sure if it is easier than the proof by Robinson.

It is available here, page 74: https://link.springer.com/content/pdf/10.1007%2F978-3-540-77566-9.pdf