The kernel and firmware on Ubuntu LTS are too old to drive your AMD gpu, which is neccessary to work since it’s a hybrid graphics notebook.
Please see this on how to install a current kernel and firmware:
https://forums.developer.nvidia.com/t/nvidia-gtx-1650-lenovo-ideapad-3-ryzen-4600h-ubuntu-18-04-hdmi-screen-not-detected/161703/7?u=generix
Once the AMD gpu is fully functional, some config tweaks have to be done to enable the nvidia gpu:
https://forums.developer.nvidia.com/t/nvidia-xconfig-doesnt-do-what-i-want-it-to-nor-does-nvidia-settings/107883/7?u=generix
this worked for me