Sorry I didn’t quite get if you got your original mainboard working again or not.
But if not, it certainly does sound like full schematics are indeed available to repair shops.
(that was from May 2022)
A note confirming that independent repair shops can get it,
An earlier blog post, if you could use an official-type announcement to point a repair shop to,
Makes it sound like they have a standard procedure set up for it.