I use a hand-me-down Macbook Pro 2012. It’s a fantastic piece of hardware. Especially after I nuked macos and installed Debian.

Yes, Matrix is the closest I’ve seen to Discord that is federated. However, it doesn’t use ActivityPub I believe

Wanted to say that I’ve used Rockbox on an old ipod classic with much success. Would recommend. You can even install user created apple-ipod-like themes to get closer to the original look N feel