How to stop steam at startup in windows 10
Solution 1:
Assuming you mean the Task Manager (if not: Ctrl+Shift+Esc 🠖 Start-up 🠖 Steam Client Bootstrapper, Right-click, 'Disable'), try disabling the Steam service:
In the Start menu, type services, and open the Windows Services app.
In the list showing up, look for Steam Client Service, Right-click it, select Properties, and set Startup Type to 'Manual'.