Quick follower to my own #102, it turns out that my machine simply needed to be started twice with the bootloader option psmouse.proto=imps set. The first time shook something looks in Gnome which resulted in a notification appearing about a minute after boot, "software update made that require restart." After the restart, when I open my Mouse & Touchpad control panel, the two-finger/edge-scrolling/tap-to-click controls have appeared (they were hidden on the first boot!) and function correctly.
Quick follower to my own #102, it turns out that my machine simply needed to be started twice with the bootloader option psmouse.proto=imps set. The first time shook something looks in Gnome which resulted in a notification appearing about a minute after boot, "software update made that require restart." After the restart, when I open my Mouse & Touchpad control panel, the two-finger/ edge-scrolling/ tap-to- click controls have appeared (they were hidden on the first boot!) and function correctly.