Anton, first many thanks for your config.plist! That kernel patch got me past the plus signs into a bootable system. Progress! However, problems still abound. I'm using a plain-Jane Logitech wireless USB mouse/KB. It's clear that the delayed/repeated/missing key presses and mouse clicks are a symptom of a larger problem in my case. Every phase of the installation stalls periodically, sometimes randomly power-cycling, and at other times simply hanging; always slow with screen progress updates. Same problems previously with my "successful" installation of HS (I'm pretty sure I lucked out to get that far).
Sorry that this doesn't help at all with your mouse/KB issues. Meanwhile, a graphics-card upgrade didn't help, but I meant to do anyway so I can use my RX560 in another Linux box.