The recommended open source driver package xf86-video-radeon is not in the repositories!
# equo install xf86-video-radeon
>> !!! No match for xf86-video-radeon in repositories.
Perhaps the author meant "xf86-video-ati"?
Apologies if this is already covered somewhere else. The forum search function WON'T ALLOW a search for "xf86-video-radeon". Why exclude terms that are EXACTLY what a user might want to search? Makes no sense!