So I'm not sure if this bug is actually a duplicate after all. I've done a fresh install of 19.04 and upgraded to kernel 5.0.0-11.12 (which supposedly fixed the other bug), and the link training issues with my Dell XPS 9575 laptop panel are still present. So it looks like the primary issue i'm experiencing has not yet been resolved.
So I'm not sure if this bug is actually a duplicate after all. I've done a fresh install of 19.04 and upgraded to kernel 5.0.0-11.12 (which supposedly fixed the other bug), and the link training issues with my Dell XPS 9575 laptop panel are still present. So it looks like the primary issue i'm experiencing has not yet been resolved.