Streaming is a continuous service. If you want that, you may actually want to consider one of the commercial options.
You could download the music and self-host a Navidrome server or something similar.
You could even do it like me and have Navidrome server in your pocket. It's natively available in Termux, so I can stream music from my phone on LAN.
But that depends on your library size.
Also... many memory cards seem to have terrible random access speed (and sadly that's something you can't know before buying it), so the initial scan may take a few minutes.