When building Arduino projects for beginners, you'll usually need both input and output sensors. However, you can come across some simple projects like the Blink example that only require an LED ...
Interestingly, he uses the Arduino IDE mixed with native ESP-IDF APIs to get the best performance. Like most complex interrupt-driven software, [Ivan’s] code uses a two-stage interrupt strategy.
Not according to [techtoys], who has created an Arduino shield that creates an HDMI output from an SPI control input. This is a project that seems to have been around for a couple of years ...