It is not super simple but I lived with outdated kernel and Xorg for a couple of years (because of Intel Poulsbo [1]). Process described in wiki [2] and uses virtualbox-host-modules as an example.

    $ pacman -Qi glibc
    Depends On      : linux-api-headers>=4.10  tzdata  filesystem

1. This version is not present in Arch Linux Archive anymore [3], search for package page [4], View Changes, search for corresponding PKGBUILD revision [5], makepkg. It is much easier if package is not that old and can be found in /var/cache/pacman/pkg/ or archive.

2. install with `pacman -U linux-4.15.8-1-x86_64.pkg.tar.xz`

3. skip package from being upgraded with /etc/pacman.conf IgnorePkg [6]

I had problems both with Ubuntu and Arch Linux updates. At least I can fix Arch Linux issues, Ubuntu felt broken.

[1] http://sergeykish.com/linux-poulsbo-emgd

[2] https://wiki.archlinux.org/index.php/Downgrading_packages

[3] https://archive.archlinux.org/packages/l/linux/

[4] https://www.archlinux.org/packages/core/x86_64/linux/

[5] https://github.com/archlinux/svntogit-packages/commits/packa...

[6] https://wiki.archlinux.org/index.php/Pacman#Skip_package_fro...

But then you can't run leading edge hardware... My motherboard's network interface, wireless interface and my gpu all require a kernel version that's newer than the 19.10 ubuntu (and even 20.04 support for stability), let alone the last LTS release.

Ukku worked well for me to get newer kernels without issue, but kvm/virtualbox were totally borked, just as my hardware support was stable.

Sorry to hear, KVM does not work? I expect problems with virtualbox but KVM, can you share a story please?

Latest Manjaro has the latest VirtualBox in the package repository. It is easier imho switch from Arch to Manjaro than going to Win10