The Servo counterpart of this meta bug is https://github.com/servo/servo/milestone/6
nox is going to knock a bunch of these out.
https://github.com/servo/servo/pull/16609 just landed, that implements the unitless length quirk, we just need to properly propagate the quirks mode in geckolib too now. I would rather let someone else do it, given the bindings are utterly confusing to me.
https://github.com/servo/servo/pull/16646 should fix at least 2 -moz-transform failures.