You can just use a relay to open and close the door if that’s all you want.

Edit: no you can't, if it's the fancy one. You gotta hack a switch like this: LiftMaster 883LM Security+ 2.0 MyQ Door Control Push Button

Sort-of: the newer ones require the physical button to speak the same rolling code protocol the remotes do. So, yes: but you have to modify a real door opener. ratgdo has the advantage that it pretends to be said door opener.

There's often a pair of pins on the internal board that you can attach a relay to. Shorting the pins causes the door to close.

That sounds even dicier than modifying the wall switch, but sure :)

There is a part of me that wants to break the damn thing open to hunt for a 3.3V line so I can power the ratgdo without a USB PSU...

bummer! i had no idea it wasn't just a dumb switch! also super cool that they reverse engineered it. :)