Is it possible to use a Calendar event as a Trigger for a Siri Shortcut? I’m trying to automate turning off the cellular connection for my iPhone every day at a specific time and it seems that a calendar event would be the best way to trigger this.
No. You’ll keep bumping into security restrictions until such time (if ever) a background scheduling system is introduced that is given permission to run these sorts of things.
I can’t imagine a third party app could do this right now given the permissions and functionality domains it would need, so I’d expect it would need to be implemented by Apple.
Fundamentally Apple have restrictions in place to help stop things consuming battery in the background and to limit the capabilities of software that may intend to act maliciously; in this case without direct foreground interaction.
At least, that’s my understanding, but perhaps there’s something I’ve missed that would offer an opportunity?