Mint was the first toe I dipped in the linux world (like a lot of people). I’m with you on Ubuntu, though I’ve played around with Kubuntu and liked it, though mostly I think I just like KDE Plasma.
Arch is definitely off the table for this: I want a media machine, not a job!
I’ve considered setting something like that up on my main homelab system. Honestly though, I only listen to audiobooks or podcasts on one device: my phone. It has TONS of storage, so I just have it set to automatically download a large queue, The audiobooks are a drop in the bucket next to the huge music library I’ve been packing around and adding to since the iPod days.