Linux support with webcams has reportedly become a major issue in regards to 12th Gen Alder Lake laptops right now, as showcased by a recent Phoronix article. Linux kernel maintainer, Greh Kroah-Hartman, says causal users should steer clear of Alder Lake laptops using Linux if they want to make video calls on their machines. Issues surrounding mainline kernel support for webcams have made webcam support almost nonexistent.
Hartman says - ironically, that Linux support with Alder Lake has been really good. But for some reason, webcams are the only exception. The lack of mainline kernel support has forced manufacturers to create proprietary drivers for their webcams.
The primary example of this is the new MIPI IPU6 webcams found in Alder Lake laptops like the Dell XPS 13 and Lenovo ThinkPad X1 Carbon. The Linux driver supporting IPU6 is completely proprietary and only supports specific kernel versions of Linux. That makes Linux kernel updates impossible, unless you want bricked webcam functionality.
This is just one example of limited Linux webcam support, with Hartman himself commenting that you shouldn't "...buy these notebooks if the vendor isn't willing to get their drivers upstreamed properly."
The main issue is that IPU6 drivers don't make use of the Video 4 Linux 2 interface, which is a common API used by webcams drivers for Linux. Instead, the IPU6 drivers rely on a different API, since the camera is more complex compared to other solutions, and vendors don't want to share any of their imaging algorithms with the public.
Thankfully, Phoronix says there is a plan for upstreaming Intel's IPU6 driver to the CAM kernel API, which appears to be a new open-source webcam API for Linux. But that work is still far and away out, with a timeline of at least a year of development - if not two years.
Basically, it appears that most of the 12th Gen laptop models sport this new MIPI IPU6 webcam, and as a result, can suffer from Linux compatibility issues due to mediocre support via proprietary drivers.
If you manage to find an Alder Lake laptop with a different webcam, there's a good chance it won't have these issues. You could always attach one of the best external webcams and it will probably have Linux support. Or, alternatively, you could have Windows as your host OS and run Linux in a virtual environment instead