I had trouble using bbswitch on my XP15 9570 running Manjaro Linux 18.04.
After some digging I found the following method in the forums to manually enable/disable the Nvidia GPU

### Requirements
- Install video-linux using mhwd `sudo mhwd -i pci video-linux`
- Then install the nvidia driver (not using Manjaro's mhwd tool, just do it using pacman) `sudo pacman -S nvidia`
- Then install bumblebee (this give you optirun) `sudo pacman -S bumblebee`

### Setup
Modify the following lines in `/etc/bumblebee/bumblebee.conf`:
- `Driver=nvidia`
- `KernelDriver=nvidia`
- `PMMethod=none`

Make sure that `/etc/modprobe.d/mhwd-gpu.conf` is empty, if it's not, delete the entries related to nvidia.
(assuming you just started manjaro and are now installing the nvidia drivers, then there shouldn't be any other non-gpu related entries)

Put the file `01-noautogpu.conf` in `/etc/X11/xorg.conf.d/`

Then we need to add the following modprobe configuration files to `/etc/modprobe.d/`:
- blacklist.conf
- disable-ipmi.conf
- disable-nvidia.conf

Then install a systemctl service to automatically disable the Nvidia GPU on shutdown,
by first putting the file `disable-nvidia-on-shutdown.service` in `/etc/systemd/system/`
and then registering the service by running
`sudo systemctl daemon-reload` then `sudo systemctl enable disable-nvidia-on-shutdown.service` in your terminal

Then add the file `nvidia_pm.conf` to `/etc/tmpfiles.d/`

Then for convenience sake add the following 2 scripts to `/usr/local/bin` so you can easily access them without typing the full script path:
- enablegpu.sh
- disablegpu.sh

Also don't forget to chmod a+rx those 2 scripts
- `sudo chmod a+rx /usr/local/bin/disablegpu.sh`
- `sudo chmod a+rx /usr/local/bin/enablegpu.sh`

Restart your machine.

### Usage
Now whenever you need the Nvidia GPU, simply open your terminal and run `enablegpu.sh` to switch it on

Similarly if you want to switch it off run `disablegpu.sh`

To actually utilize the GPU to handle the graphics of a specific application, use optirun `optirun my_cool_graphics_app`

### Tips
Also if you end up having screen resolution problems just remove `/etc/X11/xorg.conf` or rename it if you want to keep a backup

You can use autorandr to make youre laptop remember the screen resolutions settings you prefer and automatically apply them when appropriate

You can use `nvidia-smi` to check if your Nvidia card is responding/working.

You can use `glxgears` to test your graphics performance
- run `glxgears` to test your integrated intel graphics
- run `optirun glxgears` to test your discrete nvidia graphics (alternatively use the `-v` flag for a verbose output)