If you want advanced features (multiple sledders, scenery objects, and track sharing), consider Line Rider 2: Unbound (originally for PC). While no longer sold new, you can find legitimate second-hand copies or wait for potential re-releases.

You can also use web based installers like TutuApp or Panda Helper. These platforms often host cracked games that you can install with a single tap. However these apps frequently lose their "enterprise certificates" causing the game to crash or stop opening until a new certificate is issued. Is Downloading Cracked IPAs Safe?

Cracked IPAs are not vetted by Apple and may contain malware. Stability:

Downloading cracked apps violates Apple's Terms of Service and developer copyrights. It is recommended to support the developers of Line Rider by purchasing the official version. Line Rider - App Store

Since you cannot download cracked files directly from the official App Store you must use a sideloading method. Here are the most popular ways to get Line Rider onto your device. Using AltStore or Sideloadly