I am not affiliated. i use a DIN to RCA cable to run audio to my radios. This just looked interesting.
https://www.hifiberry.com/build/guides/converting-an-old-radio-into-a-spotify-streaming-box/

another one..this one is heresy however. (And I don’t mean Klipsch)
https://www.hifiberry.com/build/guides/raspberry-pi-infused-vintage-radio/

primum non nocere

.

constat

Look into AM transmitters, AES sells a kit that uses a pentagrid converter, but there's other better plans, kits, and a few commercial (low power) AM transmitters.