How to enable telephoto lens on iPhone camera?

That’s correct. One meter is too close and the camera switches automatically. I get the 4X to stay in telephoto at about 130cm or 4 ft. using Apple Camera app.

I can use third party apps (Reeflex, Halide) and force the camera to stay at 4X, but the photos are out of focus.

What app are you using, Apple’s native app, Camera, ir a third party app? Are you in any special mode such as portrait? How far away is the subject you’re photographing? The 4X does have minimum focus distance and if you attempt a photo inside the distance the Fusion Camera will switch to the 1X.

Digital zoom always uses the Fusion Camera. Manually selecting 4X forces the camera system to use the optical 4X only and it doesn’t focus that close.

Maybe this will help you --> https://www.macrumors.com/how-to/iphone-17-pro-using-8x-optical-zoom/

I don't have any issues using the telephoto camera on my 17 Pro Max. You might want to go out to YouTube where there are MANY videos on how to get the best out of the new 17 Pro Cameras.

I don't understand what you are seeing. I have the 17Pro (up from first the 15Pro and the 16Pro) and have never had an issue switching between lenses. I know when I move the phone near the subject it will automatically change to the Macro mode, but otherwise at the bottom of the screen I see the options for the various "lenses" (currently 0.5, 1x, 2x, 4x and 5x). and it will stay selected on the lens I pick (unless I hold the lens number, then the scrolling "wheel" with all the focal lengths will appear).