Typically, home theater receivers sport at least seven HDMI inputs, which should cover the majority of a user's streaming sticks, consoles and Blu-ray players. If not though, more expensive models will sometimes offer one or two more, and if you'd like to hook up both a TV and a projector, make sure that there are at least two HDMI outputs.
HDMI 2.1 is the latest standard for HDMI connectivity, with a bandwidth of up to 48Gbps. It supports gaming features that PCs, PS5 and Xbox Series X consoles can take advantage of, such as 4K@120Hz gameplay, VRR (Variable Refresh Rate) , ALLM (Auto Low Latency Mode) QFT (Quick Frame Transport) and QMS (Quick Media Switching).
While most home cinema receivers from the past two years will have at least one HDMI 2.1 output with eARC, some entry-level models only offer HDMI 2.0 input ports. But, unless you are a gamer, for most people, HDMI 2.0 will meet all their film-watching needs as it supports 4K signals at up to 60 frames per second, which no movie source currently goes beyond.