POWER8 is necessary as we are on the verge of POWER9 which will have differences and unique issues/questions. ppc64el is a good catch-all for both, but not specific enough. ppc64el is inconsistent with Ubuntu's naming convention for the kernel and other bits that support this architecture. Jorge's comment below to 'synonym' them makes sense for the case when people are coming from other OS'es where the convention is different.