I can’t get to my regal movie ap

Sorry, it is not possible, iPhone 6 is an outdated iPhone (9 september 2014), can’t be update to a higher iOS.

iOS 12.5.5 is last security updates for iPhone 6 -> released 23 september 2021.

Yes, most apps require iOS 13 or later.

Considering a newer type of iPhone?

See -> https://apps.apple.com/us/app/regal-movie-tickets-times/id502912815

Compatibility iPhone -> Requires iOS 13.0 or later.