Is it possible to completely turn off nvidia GPU to be able to run wayland?

The answer was simple: just install nvidia drivers, open the nvidia settings page and set to use the Intel HD GPU only. Login again and you are done. Works perfectly. Battery lasts much much longer and wayland works properly.

As soon as the nvidia GPU is enabled, it seems that the fan turns on immediately, and keeps running even when idle. That is probably a large part of battery consumption. I'm wondering if that is reasonable or not: is that fan really always needed?

NOTE: I recently discovered that what I described is a Ubuntu specific patch applied to the nvidia config app. Other distros may not include it entirely. Manjaro, for instance, is not including it in any way. It is probably possible to setup manually, but I didn't succeed.

I am just here to answer this question

Although I have not used a Optimus laptop for years. Bumblebee community created a kernel module bbswitch

https://github.com/Bumblebee-Project/bbswitch

You can turn off the nvidia card as long as a driver is not loaded.

 # to check status 
 $ cat /proc/acpi/bbswitch  

 # to turn off or on respectably
 $tee /proc/acpi/bbswitch <<<OFF
 $tee /proc/acpi/bbswitch <<<ON

If I knew there was a thread, I would had posted the answer much earlier.

I guess I am fighting against https://xkcd.com/979/

On some notebooks (the venerable Lenovo TP 520W being an example), one can select which graphics board to use in the BIOS setup (in this example "Auto", "Discrete" (NVIDIA), "Internal" (Intel) - IIRC).

Setting to internal will save a lot of power, make installation easier, but might impede the use of external displays.