In the Github repo there are a number of unsolved entries, and you can also make a new solution for a "solved" one – since there's no correct answer for any entry.

To see all of LeWitt's work, MassMOCA has an excellent online collection here: https://massmoca.org/sol-lewitt/

MassMOCA (in western Massachusetts) also has a wing devoted to LeWitt's work with wall-sized installations of dozens of them–highly recommend a visit!