How do I fix “Packages not in the AUR”?
$ sudo paru -Syu
:: Synchronizing package databases…
core is up to date
extra is up to date
community is up to date
multilib is up to date
:: Starting full system upgrade…
there is nothing to do
:: Looking for AUR upgrades
:: Looking for devel upgrades
:: Packages not in the AUR: linux-latest linux-latest-headers linux-latest-virtualbox-guest-modules
there is nothing to do