Discord recently updated their back end. Since then it broke a lot of ppc clients and the web app on older browsers. Right now there are only a few options left for discord on powerpc. Some require Leopard, the others require Linux.
MinDisc (requires Leopard),
Bitlbee (requires Leopard). On powerpc Linux you can use the current webkit based browsers like Eolie or Surf for the web app, Pidgin with discord plugin, or again Bitlbee is also available as well.
Cheers