I was reviewing the FSM covering up to 2021 and from when you look at the fact the Driving Support Switch ECU was removed and all troubleshooting in manual points to the skid control ECU I think a '20-'21 Luxury owner (w/o off-road package may need to make a "costly experimental and untested purchase" of 89541-60C10. This may also not be all the puzzle pieces to make it work either so throwing that out there.
20-21 base & premium are going to need some substantial wiring even if this replacement skid control ECU works for Luxury trim.
I can't seem to pull up any info about 89541-60C10 in parts schematics even though we have a picture and report of it's present on '20 Luxury w/off-road package.... so I have asked one of the Lexus/Toyota parts guys help me look into on his side.