Look at Fiio. They're a Chinese company that makes pretty good quality mp3 players. They have some expensive models but also a few for less than a hundred bucks. I've owned two of them now and love them.

You can just drag and drop files onto a microSD card and then the player will recognize that new files have been added. It's super simple to manage and no iTunes or other software required.

Edit: The M5 and M3 pro both use a proprietary OS. The M6 is android based so you can also load Spotify/YT music/tidal/etc. These models are all touchscreen. If you want one more old school without the touch screen, they're m3k model is still on aliexpress. And they used to have models with scroll wheels (I dont remember the model number) that I'm sure you could find used on ebay or something.