I had that same problem creating my respin with Mate, in this thread they helped me to solve it,kultex wrote: Fri Feb 19, 2021 8:07 am
EDIT: the "su-to-root" problem is because of the change from policykit-1-gnome to lxpolkit - still no soiution
viewtopic.php?p=609556#p609556
Best regards from Senpai