>I'm not buying a phone with 512GB-1TB of storage just for my music,

If a 512GB phone costs you $300 dollar more tahn the one you would have bought, it amounts to $2 per month for a 5-year phone. Spotify is three times that.

$300 will also get me a used mini PC[0] with 2TB of storage[1] I can set up at home in an evening with Navidrome+Audiobookshelf and not have to buy a phone with massive storage at all! :D

And as a bonus everyone in my family can listen to the same collection without having to upgrade to a 1TB phone. And I can use the same source in my car, on my laptop, desktop etc. All without having to waste 400GB of space for music storage on every device.

[0] https://www.ebay.de/itm/156667490633

[1] https://www.ebay.de/itm/296887285188