How can I get a track ID from a track URL using the SoundCloud API?
I know this is kinda late but i faced the same issue yesterday and found a new (undocumented) endpoint that you can use.
https://api-widget.soundcloud.com/resolve?url=SOUNDLCOUD_URL&format=json&client_id=CLIENT_ID
You can find your CLIENT_ID by looking at the Network Inspector in the DevTools and select the XHR filter while browsing the SoundCloud website.
I think this is sufficient until the official APIs are usable again.