MarsSeed [1] filed a deletion request for virtualbox51-guest-iso [2]: Orphaned legacy package, last updated in 2018. Even VirtualBox 5.2 is EOL since July 2020, it fails to build and install on Linux 5.8 and newer. (The earlier virtualbox 5.0 and 5.2 AUR packages just got deleted for this reason.) There exists a VirtualBox 6.1-based guest addition ISO, downloadable from official site. Also Arch [community] carries that package: https://archlinux.org/packages/community/any/virtualbox-guest-iso/ This orphaned package is therefore not needed and might not even work correctly. [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/virtualbox51-guest-iso/