Posting this in order to answer it.
Trying to uninstall programs in Discover a message appears saying “You have no Authorization to execute this operation”.
dnfdragora opens but then starts to crash.
Fixed as said here.
Edit /usr/share/polkit-1/rules.d/org.freedesktop.packagekit.rules
Change
if (action.id == "org.freedesktop.packagekit.package-install" &&
to
if (action.id == "org.freedesktop.packagekit.package-install" || "org.freedesktop.package-remove" &&
Initially I had also done as said in another post related to the linked one:
chown polkitd:wheel /etc/polkit-1/rules.d
chown polkitd:wheel /usr/share/polkit-1/rules.d
but that was not enough.
After editing the file /usr/share/polkit-1/rules.d/org.freedesktop.packagekit.rules (which also fixed dnfdragora) something happened which I don’t know whether was related to this action: after reboot the plasma desktop would no load. I have fixed this by rebooting, initially selecting the “restore” (third entry) option in the grub list, then booting in the normal way (selecting first option).