On 2018-12-19, Fred Smith <fredex at fcshome.stoneham.ma.us> wrote: [...] > Result: Boots to GDM just fine, but Mate is a black screen. Switching > to Gnome, works fine, but I can't stand Gnome. Not knowing what else > to try I restored the dd backup. This is a known issue, and was mentioned on this list recently. The problem is that Mate in EPEL needs to be updated to work with CentOS 7.6. Perhaps keep an eye on changes to the EPEL repo before attempting the upgrade again.