Do smart water shutoff valves require professional installation?

It depends on the type. Inline whole-home monitors like the Moen Flo and Frizzlife splice into your main supply line and most reviewers recommend a plumber unless you're comfortable cutting pipe. DIY over-valve systems like the YoLink kit clamp a motorized actuator onto your existing quarter-turn or gate valve and can typically be installed without cutting any pipe, which is why verified-purchase reviewers favor them for renters and the less handy.