I have one of these hidden units to install for 99% of my listening.
https://www.memphiscaraudio.com/product/smc2a/ It is kind of like the bluetooth amps mentioned but I can use my own amps and components with it. It can be installed without the hardwire controller if you only want to use your phone. My original working AM/FM will be installed in the dash with the new speaker I purchased.