Yocto Project

The Yocto Project isn't something you download and boot -- it's a set of tools (centered on the BitBake build engine and a large collection of 'layers' describing how to build specific packages and board support) that hardware and product companies use to construct their own fully custom embedded Linux distribution tailored precisely to one device's hardware and software requirements. It's genuinely foundational infrastructure across the embedded industry: countless commercial products, from networking equipment to automotive infotainment systems to industrial IoT devices, are built using Yocto under the hood even though end users never see 'Yocto' branding anywhere on the finished product. It's the closest thing to an industry-standard toolkit for the 'build a completely custom embedded Linux' problem that T2 SDE and Linux From Scratch address on a smaller, more hobbyist scale.