You can become a Patreon member and download many of the YouTube fields onto your device. Then play those downloaded fields through your music player of choice (mine is VLC Media Player–no affiliation–if you’re wanting suggestions) without using any data as you play them. (You will, of course, have to use some data to download the files initially but they’re mp3’s so the files are relatively small.)
If you’re curious, we have a very up-to-date (thank you, @uial and all!) Patreon Uploads List of the files available on Patreon, so you can check it out and see if that’s a path that’s right for you.
Additionally, you can listen to YouTube videos through VLC Media Player, but that will still use your data.
If you have more questions of this nature, maybe you want to start your own thread or post them in a thread that’s on that topic, as we’re sort of derailing this thread from its topic of “How many fields can I listen to?”
Hope that helps.