I'm definitely interested in finding this out too.
Ability to share canvas to Public Gallery, Collection, Social Media platforms - can be removed (individual options or all) through script placed in production.js file from Alteryx installation drive.
I can share the instructions and steps tomorrow with screenshots. In the mean time, feel free to reach out to support@alteryx.com to obtain the instructions.
Thanks @revathi , I confirmed with Alteryx...looks like your solution is the only way forward for now. No worries about providing me with the script, they provided me a pretty detailed walkthrough.