Maybe I'm too old, but I prefer to listen music on a portable players instead of a smartphones. Firstly, the quality in a smartphone may be inferior, secondly, convenience - the touch screen is not very suitable for control.
At the moment, I use a rather rare example of e.Digital MXP 100 around 2000, with a chip from Texas Instruments and with Compact Flash or MicroDrive as a storage. It even has voice control, you press a button, name a song and it starts playing, cool even for 2000!
I bought it second-hand without a battery, but at least with a charging cable. All ports here are proprietary, no micro or mini USB. I picked the only USB data cable that fits the shape, from a Casio camera. I picked the new battery based on voltage and amperes, I had to change the connector, fortunately I cut off the connectors from old junk earlier and collected them in a box, one matched.
I managed to find with difficulty, having sorted through dead links, one live one with an application something like Music Explorer, since simply placing files on the card will not give anything, the player requires the creation of technical files with a list of your files, the manufacturer decided to complicate the user's life. Well, as expected, the application is glitchy, it sees the player and is even ready to change files on it, only immediately after the change it crashes and the maximum it gives is to create an empty file or folder. And this is independent of Windows (tried in Win98, 2000, XP - all the same, probably some libraries are missing). I had to write a PHP script that creates a ready-made technical file with certain bytes from a list of files and only then can you play files downloaded independently to the card.
The sound quality is very good, no worse than the slim player from Sony, large buttons, in short, in the end I am happy and consider the quest completed.
Doom is what you want (c) MAZter