Time ago i re-watched the animated short Rise and Shine, and i noticed a particular thing:
https://i.imgur.com/Tcrsult.png
Look the monitor on her left, does that boot screen looks familiar?
https://i.imgur.com/sxkkMJL.png (booting my Debian VM, after time i discovered it used systemd)
https://upload.wikimedia.org/wikipedia/commons/thumb/8/87/HP-HP9000-715-100-Workstation_03.jpg/450px-HP-HP9000-715-100-Workstation_03.jpg (actually SysVInit)
https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.linuxandubuntu.com%2Fwp-content%2Fuploads%2F2019%2F07%2Ftrueos-uses-openrc-init.jpg&f=1&nofb=1 (OpenRC init system)
I can tell probably that PC uses a system derivated from Linux or UNIX
Plot twist: they are all init systems (the first process in a UNIX system, to make operative the system)