I spent a little while going after “the freakish horrorshow that lives under the keyboard” of my childhood Apple ][+, and I have two comments. First: to the extent that I’ve managed to lift it off, it appears at least as if the PCB below is undamaged. Second: that is some stubborn goop. I’ve been soaking it with isopropyl alcohol and scrubbing it with Q-tips, and eventually a lot of it came up. The picture below is more of a progress report than a completion report, there is still enough around the edges and between a couple of chips that I still want to clean further before I run power into it. I’m a bit concerned about what might be under the chip sockets, too, so I may ultimately pull those chips out and try to clean inside as well, though given the stubbornness of this whatever-it-is I think it’s pretty unlikely that I’ll ever be able to get all of it up.