The default Ubuntu 20.04 kernel is 5.4. It’s a bit old, sure, but that’s what the distro decided on back then. Canonical keeps pushing patches into that 5.4 line too. That said, the Ubuntu 20.04 repos do actually have a 5.6 kernel in them, named linux-oem-20.04. You can just install it. sudo apt install linux-oem-20.04 So what’s this kernel for? Canonical’s official explanation is that it’s “a kernel with some drivers and tweaks for certain OEM vendors’ devices” — if you’re installing on a laptop or desktop that’s been “Ubuntu certified,” there’s a decent chance your drivers are sitting in this kernel. Mine’s a ThinkPad, so I’m definitely fine.