I just restored a new computer (same model/10.13.6) manually from a backup and it looks like subpixel rendering is now busted on my external display. Does anyone have any ideas?

I just restored a new computer (same model/10.13.6) manually from a backup and it looks like subpixel rendering is now busted on my external display. Does anyone have any ideas?

that was changed / removed from Mojave but you mention HighSierra so not sure if they are related in any way