How about the free DND (DoNotDisturb) [0] by Objective See foundation?

[0]: https://objective-see.org/products/donotdisturb.html

DND is a valid alternative! There's definitely overlap, including photo alerts. DND's detection is based on opening a MacBook's lid.

Someone Was Here also detects activity after idle, lock-screen interaction, and unlocks, so it covers an already-open laptop or a desktop Mac that has no "lid" as well.

It also recognizes your face locally to suppress alerts about yourself, and offers a multiple remote alert options, Shortcuts actions with Siri phrases, a webhook for integration, and an MCP server for agents.