HA has add-ons and integrations to add functionality, including the use of GPIOs. Which you need will depend on what you want to use the GPIOs for. Unfortunately there is not a one-stop-shop summarizing all the options, so it will take some research to find the right option.
I found these with a quick search, hopefully this is a starting point to find what you need:
- an integration for binary sensors, switches, and covers
- an add-on to use GPIOs for PWM e.g. for a fan speed control
- an add-on to use GPIOs to connect i2c bus devices