i use a feature phone / dumbphone that has an sd card slot. load up the sd card with music, and the player is super simple and works great for me. bluetooth earbuds work too, but the rechargable battery of mine died after owning them just a few months longer than the warranty lasted, so i'm back to using wired earbuds (with a usb-c to 3.5mm adapter, do NOT buy the cheap shit from temu, get one that actually sounds decent).

the phone was like $50, and a prepaid sim card inside it makes it so i can use it as cheap backup texting/calling device too when i want to disconnect from all the bullshit the smartphone comes with for a while (still trying to get fully rid of smartphones but it's very hard these days)