@Sergio

Your only hope of multi-booting on an AGP PowerMac is to obtain an Apple-Firmware Radeon AGP card. Please don't go and buy cards that will not work. Even if you somehow managed to obtain a PCI card that would work on MorphOS (Voodoo? :) the performance would be many times worse than that of the AGP card.

It would have been a different discussion if you had a PCI Express G5.

A card you need isn't super hard to find on ebay, https://www.ebay.ca/itm/234789401059 for example.