Could be a bug. You can also use the screen recording option from the quick settings panel (if it is not removed then) until this bug fixes.

It might be available on quick settings, if not edit quick settings, find "screen recording", add it to the quick settings. And done

App lock was earlier on old samsung phones, it still exists on some samsung phones (2017 - 2021 models) but it is a hidden setting.Use an app like shortcut maker(in play store) to open the system app("app lock" application name: App lock)

It already exists (on newer models), just get a new samsung phone