There is more to it than that, when the wheels contact the runway the oleos retract and start a chain of events. The brakes come on and the engine reverse thrusters actuate to slow the aircraft.

The wheels have to touch the ground and start spinning to start this sequence, the altimeter doesn't do this. Murphy's law.

All automatic flight control can be over ridden by the crew, they just touch the controls and that overrides them. They have full control while landing anyway.

As for 5G, no one really knows what might happen, the FAA is requesting that any 5G towers near airfields will be disabled permanently.