Most of projectors is connected to the external device by HDMI ports. And there are two kinds of HDMI ports: HDMI Inputs and HDMI outputs.
HDMI Inputs is a received end. It can receive audio and video signals which are transferred from the HDMI outputs devices, such as Blu-ray players, game consoles, etc.
HDMI outputs transfer audio and video signals to the HDMI input devices, which receive and process them.
For example, the HMDI output of a Blu-ray player could be connected directly to a TV's HDMI input and you can see the video of a Blu-ray player on the TV after connected.
HDMI port of the realme Smart TV is the inputs port and it only supports receiving the signal, not sending the signal. It also can't send the signal to the projector to cast the TV screen.