https://www.stereotool.com/Stereo Tool is a professional low latency audio processor that is used by over 1000 FM stations, thousands of web radio stations and AM, HD and DAB+ stations all over the world, by musicians who use it to process their recordings, and by hundreds of thousands of people who use the free version¹ to listen to music on their PC.
Download: https://www.stereotool.com/download/
Stereo Tool can generate an MPX signal, including stereo and RDS data, which can be sent to the FM transmitter using a good quality 192 kHz capable sound card. No separate hardware stereo coder or hardware RDS encoder is needed.