It looks like my only current option is to go into each cPanel→Softaculous to each installation and edit it. Is there a way to *globally* set ALL WordPress installations on the server to autoupdate WordPress + plugins + themes?
Unfortunately, the keywords I've been using to try and find this answer tell me lots of lovely and otherwise useful things, like how to enable this for a single installation, or how to disable autoupdates, but I haven't found the answer for my question yet. :(