https://www.open-electronics.org/sprout-the-open-source-motherboard-that-brings-ipods-back-to-life/

Sprout is an open source replacement motherboard that brings third- and fourth-generation iPods and the iPod Mini back to life. It installs without soldering and reuses the original shell, monochrome display and click wheel. In place of the old electronics come Bluetooth, USB-C, a high-fidelity DAC and microSD storage. The project is by Certain Things and blends the tactile nostalgia of early-2000s Apple design with today’s connectivity: a dedicated music player that does one thing, but does it well.

Assembly doesn’t require a soldering bench. The board takes the place of the original logic board inside the same shell, so the display and click wheel stay the ones you already have in your hands.

https://www.crowdsupply.com/certain-things/sprout-pi-mainboard

https://certainthings.studio/sprout/