Recently I bought a usb-c empty external monitor card to prevent mac from going to sleep. There are many of these external monitor simulators on Amazon.
I still see the laptop go to sleep many times with the external monitor simulator.
This is the one I bought.
4K 60Hz USB-C Type-C Virtual Display Adapter DDC EDID Dummy Plug Headless Ghost Display Emulator 2K 60hz1080P@120Hz