I was looking at the Pico first when writing that, but you would need a SD card header. Small issue - I use one for my Dreamcast controller Maple>USB bus.
On top of the lower power consumption, another advantage of the pico is that you can actually buy the raw RP2040 or RP2350 chips (for roughly $1) and make your own custom PCB.
You may need to build it yourself, but it looks like everything a HN-using MP3-buyer would want.
I checked, the 2nd gen iPod mini can get 18 hours of listening on a 400mAh battery, with a spinning HDD. This is getting 20+ hours listening with a 2200mAh battery and solid state storage.
Not that 20+ hours of listening is bad, I just expect a player with a battery that large to do quite a bit more.