2.29.0 — constraints that drive another object now work
A VRC constraint can sit on one object and drive a different one, through its Target Transform field. Unity's constraints have no such field — they always affect the transform they're attached to — so AvatarBridge reported that as an unsupported feature and dropped the redirection.
Dropping it isn't a degradation. It's a silent, total failure of anything built that way.
Why it matters
Avatar Limb Scaling is exactly that shape, and it's far from the only prefab that is. Its scale constraints live on proxy objects inside its own prefab and point at the avatar's real arm and leg bones — that's the whole mechanism. With the redirection dropped, each constraint scaled a hidden proxy instead.
The result was an avatar where the Arms and Legs sliders appeared in the menu, moved, and synced correctly — and changed nothing anyone could see. The tester reasonably asked whether they were dead weight. They weren't; the conversion was.
The fix
Unity offers no way to redirect a constraint, but it doesn't need one: the constraint can simply be added to the target instead, carrying the same sources. That's exact rather than approximate, and it's what now happens.
Those report lines change accordingly — from Approximated: 'Target Transform' redirection is not supported to Converted: the Unity constraint was placed on that target instead.
The one case still dropped
A Target Transform pointing at something outside the avatar. That isn't ours to add components to and wouldn't survive an upload either way. It still drops, but the report now says plainly that whatever it was driving will not move, rather than describing it as an unsupported option.
Confirmed in game. If you converted an avatar using Avatar Limb Scaling — or any prefab whose constraints drive bones from proxy objects — it's worth re-running on this version.