I don't have an answer but am also interested in reducing understeer!
Based on previous experience with my Miata, factory alignment is biased towards understeer intentionally for legal/safety reasons. Adjusting that alignment can completely change the handling balance and often make more of a difference than stiffer sway bars (and doesn't compromise ride quality)
There were a couple of Miata focused companies who tested and published recommended alignment numbers for street, autocross, track, or mixed use but I haven't seen anything similar for the F56 chassis.
Anyone know what adjustments there are from the factory? My Miata had independent toe, camber, and caster both front and rear so I was a bit spoiled. I think the F56 only has toe in the front and probably toe and camber in the rear? (I see some eccentric bushings)