And I'm not talking about the codec. I am talking about the fact that you pretty much need iTunes in order to use the iPod. And they also had their proprietary charging port. 2 huge fails.
iTunes or ... Floola, or AmaroK, or gtkpod, or gPodder, or Rhythmbox (this is the one I use, to manage music on my iPod Mini, in Lubuntu), or aTunes, or Yamipod, or Banshee, or ...
The first iPods used Firewire, an IEEE standard: https://en.wikipedia.org/wiki/IEEE_1394
Later iPods used the 30 pin connector, which was pretty trivial to unwind (https://pinouts.ru/PortableDevices/ipod_pinout.shtml), and could be sourced from any number of sources. It's also worth remembering that, at the time, pretty much *every* device used a different proprietary connector (looking sideways at my old Palm Treo, Palm Pilot, Samsung and Motorola flip phones, etc), or had basic connectors (SanDisk MP3 player with a Mini USB B socket) that could *only* be used to manage the media, with no audio transmission or playback control etc.