Need help with nvidia graphics (Gnome)

I got my hands on a Dell Inspiron 7591 with Intel UHD graphics and a Nvidia MX250. I installed EOS with the latest ISO (online installation with systemd-boot and dracut) and ran
nvidia-inst --prime
On the gdm login screen the “cog wheel” to choose between gnome and gnome under Xorg was missing and Gnome was running under Xorg by default. I found some threads about this problem and a recommendation to execute
sudo ln -s /dev/null /etc/udev/rules.d/61-gdm.rules
and it worked.
How do I proceed to toggle between Intel and Nvidia graphics? What packages are recommended for this setup? Envycontrol?