As the name implies, suspend is fixed in the C720/Peppy ROM’s. Turns out I had forgotten to conditionalise/remove something from the board’s DSDT, which I didn’t forget for Falco/HP Chromebook 14.
Additionally, I have updated all the other Haswell Chromebook ROM’s to make sure the DSDT is suitable in those.
Jeltka has also had i915 frame buffer support added, so even if something is wrong with the graphics ID/ROM, you can still easily get the display to work. There’s probably something else in there which escapes me, but that seems like enough for the moment.