Ah great you got it working, adding invy hadn’t worked for me. But with your success I’ve revisited, physically rotated the screen (!), swapped rotate to ‘left’ in the conf file and then applied the same as you …
lcd_rotate=2
dtoverlay=vc4-kms-dsi-ili9881-7inch,swapxy,invy
and now it works! The upside to those issues is that I discovered my old iPad from 2012 can be used as a VNC controller, which is v satisfying.
Thanks also All!