Option to save custom internet radio stations independently of TuneIn or other services

I may have overlooked this feature, or there may be another way to save custom radio URLs independently of TuneIn or other services. In general, I'm fine with saving custom URLs as favorites on TuneIn, but since the free TuneIn account has this annoying behavior of losing the connection by invalidating the authentication token, and I have to log out and log back in every few weeks to continue listening to Internet radio stations, this is not an acceptable solution for me. It would be great if you could save a few URLs (~20) locally and use them as favorites and presets. This would help users listen to custom stations without interruptions using a paid device, without being dependent on a streaming service. It would also improve data privacy.