At the very least, I wish Digital Radio Mondiale won out over DAB. It’s designed to use the existing long, medium and short-wave bands and can even co-exist with an AM broadcast. I imagine digital radio would work quite well with the propagation characteristics of the mediumwave (and longwave) broadcast band.

There’s also DRM+ for the VHF band, including the FM broadcast band.

https://en.wikipedia.org/wiki/Digital_Radio_Mondiale