Any way to use the old 30-pin adapter with an iPhone 15

OK, I know that the 30-pin adapter is dinosaur technology, but my car head unit has one, which until I upgraded to an iPhone 15, was used to play Pandora off my old iPhone through the head unit via either a lightning to 30-pin cable, or the lightning to 30-pin dongle, both of which worked flawlessly.

OK, so after upgrading I though (maybe) all I need is the Apple lightning to USB-C cable. Wrong. If I have the lightning to USB-C cable plugged in the iPhone, then when I plug in the lightning side of of my 30-pin to lightning cable or dongle, with nothing connected to the 30-pin, the iPhone complains: Accessory not supported. Obviously it complains the same when connected to the head unit.

All the cables are genuine Apple, and not the cheap Chinese knockoffs.

Is there any way to connect an iPhone with USB-C to an old 30-pin. I know I'm not the only person with this request, because there's a gazillion old music stations that rely on the dinosaur.

Cheers.