I haven't had an nVidia laptop in ages: on the desktop linux + nvidia drivers works just fine most of the time, even on rolling release distros.

laptops are very different since they have two gpus, one internal panel, possible external monitors, and any permutation of wiring of gpus to panel/monitors, battery and thermal constraints, screen tearing issues, etc. Stay away.

Why does that combo go wrong in a laptop?

Because nvidia optimus drivers are not open sourced and a huge PITA in some linux distros/desktop environments who wish to stay as FOSS as possible.

Not a problem on desktops since they don't have optimus but on laptops without a proper optimus implementation for linux you'll end up with your 1660TI or whatever running at full blast with just your terminal opened, killing your battery in no-time and turning your laptop into a frying pan.

That's why linux devs prefer no nvidia dGPUs on their laptops.

It's not just a foss v/s proprietary issue. Clarifying for the OP. Even with the blobs, it's a subpar experience due to the optimus madness.

I gave my MSI Ghost Pro 4K gaming laptop to my mother to browse the internet and bought an XPS. For her, in windows, it works ok, and if she launches anything that needs the Nvidia card it'll enable/disable as required.

Using that laptop in Linux was the bane of my life, Optimus is hell and if you want to switch between Intel/AMD you need to reboot, no thanks.

You can't use it for VR if you have the type of Optimus I had, where if the display was connected to the Intel rather than to the Nvidia, it wouldn't work. If you left Nvidia on, and tried to use it as a laptop, you'd be lucky to get 20 minutes battery life (not exaggerating), so it was neither great for gaming nor useful for productivity.