The Google Pixel 6 and the Pixel 6 Pro are the first smartphones powered by the company's in-house Tensor SoC. They also shipped with Android 12 out-of-the-box, and if you take a look at the kernel sources, you can find Linux kernel 5.10 under the hood. If you’ve already bought either device for the sake of aftermarket development, then you’ll be happy to know that Google has recently started populating a mainline Linux kernel 5.15 branch for the Pixel 6 family. What's more interesting is that XDA Recognized Developer Freak07 has already managed to compile and boot the mainline kernel release for the device duo.
What's so exciting about having mainline Linux kernel support for an Android device? In a nutshell, this is kind of similar to how Project Treble modularized Android by separating the OS framework from the vendor implementation, but with a lot bigger scope. With a successful inclusion in the mainline Linux kernel, the Pixel 6 family will be able to boot future kernel revisions released by Google (or kernel.org) with no changes, which makes it a lot easier to keep up with AOSP versions, or even vanilla Linux distributions. End of the day, this is the true essence of the Generic Kernel Image (GKI) project: Isolate SoC vendor and OEM customizations to plugin modules and eliminate out-of-tree code, so that Google can push kernel updates directly to the end-user.
Google Pixel 6
The Pixel 6 comes with Google's new Tensor chip, a modern design, and flagship cameras.
Google Pixel 6 Pro
The Pixel 6 Pro is the larger sibling that comes with Google's new Tensor chip, a modern design, and an extra telephoto camera.
With that being said, keep in mind that the whole mainline kernel for the Google Pixel 6 is nowhere near the stable tag. As pointed out by Freak07, Google has also laid the foundation of a common Linux kernel 5.15 for Android 13, which might be related to the upcoming major kernel update for the devices alongside the next Android version bump, or it could be entirely intended for a future Pixel device.
Google Pixel 6 XDA Forums ||| Google Pixel 6 Pro XDA Forums
Nonetheless, you can boot the mainline Linux kernel 5.15 on the Pixel 6 and Pixel 6 Pro right now without messing up with the code, thanks to the proof-of-concept kernel build offered by Freak07. According to the developer, a number of things like Wi-Fi calling and audio output via USB-C are currently broken, but if you can overlook those, you can have a first taste of the latest Long-Term Support (LTS) Linux kernel on your phone. To learn more, check out the XDA thread linked below.