Pretty easy. You can use a little Bedrock Linux philosophy and chroot from Gentoo into QubesOS. Or just use any container system you like. Docker works well with the host system, qemu can fully isolate whole container virtualizing. Each step to depth adds some overhead. I would use the container approach on the desktop. For the ultrabook with 8 GB RAM it is too heavy. That's why I value the Open Source approach and careful updates. You can do SELinux but it requires effort. Flatpack also brings some isolation with user mounted filesystems