I want Homebrew enabled, so that I can Homebrew items for my games, except they all have random cantrips like "Alter Hair", "Can't Trip", "Facepalm", and "Leaf into Dagger". These aren't say, broken, but they do not fit in my campaign and I cannot figure out how to remove them. I've tested it and they do not appear when Homebrew is disabled, and I have tried keeping it enabled but disabling all of the adventures and sourcebooks so it isn't that. Why are seemingly random cantrips etc. appearing in their list of available-to-learn spells?

Someone in your campaign has homebrewed those spells, and all homebrew in everyone's collection is shared with the campaign. Ask your players and find out who made them, and suggest that they remove those Creations from their Homebrew Collection so that the spells don't show up for everyone else. (They'll still stay in Creations but not show up in character sheets.)