Turning off GPS and turning on airplane mode should do the exact same, right? If you don’t trust your OS you could use something like GrapheneOS or LineageOS, that’s what I do. I don’t feel the need to physically stop my phone from collecting data if it’s Operating System is free software and built to respect my privacy. That way my smartphone actually does what I want, instead of working against my interests. Constantly fighting against the device you carry all day sounds exhausting.