If you like snacks and will visit Gettysburg, I’d visit nearby Hanover with their Utz chip factory tour and the Snyders, Renovah, and Utz outlet stores.

There’s tons of Amish and Mennonite stuff in Lancaster County, and especially if you are Christian I would highly recommend the Sights and Sounds Theater and watch one of their amazing performances (I say this as a non-Christian). (Btw Lancaster is pronounced “Lang-custer” here)

In Harrisburg, the National Civil War Museum is huge and great if you like history, and getting a tour of the state capital building is pretty neat too (beautiful architecture imo).

In Reading, they have a cool pagoda you can visit that overlooks the city. I am unfamiliar of other cool sites to see that are somewhat safe, but I am sure someone else can steer you in that direction.

Lebanon does have a history museum (Stoy Museum in the historical society) but it is nothing compared to Gettysburg or Harrisburg, and idk if there really is any other tourist draw to the county unfortunately.

In general though, as someone from between Annville and Ft Indiantown Gap originally, I would say your best bet to just find something cool to do as a tourist outside of Gettysburg would be in Lancaster County, as they have been a hot tourist destination for a while with a diverse amount of things to do, especially if you like learning about the plain folk groups.