Yes, changing display resolution nowadays to a non-native one isn't exactly desirable, and on mobiles it isn't even possible.

Therefore, for a project that was made for a fixed resolution, there are two ways to handle this:

1. Rescale everything in code yourself (might require significant development effort).
2. Render everything to a render target (check Tunnel example to see how you can use TBitmap for that) of fixed size, e.g. 640x480, then simply draw such render target to fit whole screen, which would take care of scaling and simulate older behavior.