Do I need a separate grinder for a home espresso machine?

For semi-automatics without a built-in grinder, yes. Specialist communities like r/espresso repeatedly stress that grinder quality matters more than the machine itself for shot consistency. Machines with integrated grinders (Breville Barista Express, Ninja Luxe Café, CASABREWS MARENZA) bundle this in, but the built-in grinders are typically the weakest link compared to a dedicated unit.