I asked almost the same question a couple of days back. add-radio-station-t3883.html
Maybe it helps a little. I assume you have started a ssh connection with your Raspi. Now type
Here you get a list of all radio stations that came with the installation as default.
Now you are in this directory, choose several of the station files and open them with nano one at a time. Do not change anything just have a look. You get a picture of a starter for a station, some are special but you will see the standard.
I copied one of them to a different name. (If you are not familiar with Linux the command is mv). Then I opened the copy with nano and edited the
existing Title (name of station) and the URL. After saving I rebooted and found this station in the browser of the main screen, started it with Add and Play and it worked perfect.
As Mobey Duck told you the URL is not the m3u file but something like streamXXXXX
I got this URL from the website of the radio station I wanted to add. Funny, they had an m3u file that I clicked on to get the wanted URL. Don’t ask me if this works on your station(s) or if they have other ways to distribute it.
I hope this info helps a little. Don’t give up Volumio is absolutely worth trying.