Does Linea require an Apple Pencil?
The short answer: No, not at all!
The long answer: Linea for iOS was designed from the ground up to harness the power of the Apple Pencil and the iPad Pro. However, not everyone owns this powerful combo and we recognize that. The good news is that you can use your finger to draw on supported devices.
While there is no formal list of supported styli, you should have no trouble using one with Linea.