Comment 49 for bug 1571416

@john This problem was meanwhile worked around by setting radeon.agp.mode=-1 as default in recent kernels (=> 5.0 ?). So you don't need to fiddle around with your settings here. Unfortunately Ubuntu ppc support is dead, only ppc64le option is maintained.

But there are other distros (Void, Adelie). Void has very good ppc support, a working Firefox 72 for ppc64 and working epiphany browser for ppc. Also live images are avaiable: https://voidlinux-ppc.org/