As they said --air-gapped smartphones are much safer than the air-gapped PC which are vulnerable to hacking, did you know that even fully air-gapped PC can exfiltrate information through the output radio signals generated by the computer or call [electromagnetism].
Also expert says that through [ultrasonic waves] a virus can be used to steal the private key out of the computer.
Unless you're high profile person, very important person or letting people know you're extremely rich, worrying about this kind of vector attack is pointless. Additionally, this kind of attack is also theoretically possible on mobile devices.