Ninite, Chocolatey, Patch My PC, Snap Store , Synaptic, GNOME Software, GDebi, pacman (package manager), UpdateStar, AppFresh, Software Informer, UpdateHub, Ubuntu Sources List Generator, Ubuntu After Install, OUTDATEfighter, Kaspersky Software Updater, bauh, Oduso, Ketarin, Debian Sources List Generator, Aktualizator, Update Notifier, PostInstallerF, Appvers, CoApp, R-Updater, Updapy, Brothersoft Updater, Vulmon Alerts are some alternatives to Update Manager.