Long story short, the vast majority of laptops don’t support passthrough, and even the ones that do make it incredibly painful to set up. Even then, not all guest operating systems will work, even if you can get it working for one of them.
There are 2 methodologies for enabling passthrough in Laptops:
Older laptops (or newer models that don’t have bios whitelisting) can attach a desktop GPU via the mPCIe or m.2 slot normally reserved for a wireless adapter or NVMe drive using a variety of adapters. These don’t typically give the full bandwidth needed for 100% baremetal performance but they’re the most compatible with traditional passthrough methods. Laptops that support expresscard or pcmcia also have this option available, but are usually too old to be relevant.
Thunderbolt laptops also have tentative support for this, but it varies by model.
This category of passthrough is a lot more dependent on your laptop’s native hardware configuration. Older models with MXM based GPUs can work, but newer “optimus” models depend entirely on the implementation of their intel/nvidia GPU muxing. If your bios does not support manual override of one GPU or the other, chances are it won’t work. If it does, and you have physical ports dedicated to the discrete gpu only, then you may be good to go with some extensive tweaking, but there’s no guarantees.
Search https://www.reddit.com/r/vfio with your Laptop’s model to find specifics.