In addition to the major online music services (YouTube Music, Spotify, Pandora, etc.), I really like
RadioParadise.com. I've been listening to them for over 20 years. They've got apps for Android and iOS, as well as some of the home assistant and home audio automation platforms.
If RP's repertoire happens to match your taste, then it might be a good alternative for offline listening. Their Main Mix has introduced me to a lot of music I'd never have come across otherwise. There are also channels for Rock, Global, and Mellow mixes. You can download hours of any or all of those channels for offline listening (limited primarily by your device storage and download speed).
You can also rate songs, and then download hours of "My Favorites" for offline listening. Of course, you'll get more variety in your "My Favorites" stream after you rate plenty of songs. (After 20 years, I've rated plenty, and rarely hear a repeat even on long trips.)
RP is listener-supported. There are no ads and very few "station identification" breaks. I kick 'em some cash every month because I like what they do, but there's nothing to stop you from being a total leech if you want. You don't even have to create a (free!) online account if you don't want to, though you won't be able to rate music and create a "My Favorites" offline playlist if you don't.
RP's a mom-and-pop operation started by a former radio DJ and his wife. The originator has been edging into retirement for the last year or so, but his daughter has been taking over the reins and so far the transition has been very positive.
RP is somewhat like a traditional radio station rather than a streaming library. The songs play in a sequential order; you can't replay a song or search for a song and play it on demand. When playing downloaded music, the cache size decreases over time because songs are deleted after they're played. The one difference from radio: If a song comes on that you don't want to hear, you can hit the "skip track" button and move directly on to the next song. (This behavior applies both to the live streams and to downloaded playlists.)