How can i use ea ESP8266 to make smart buttons

Hello,
i have a few devices in my room like my monitor, where i want to make the buttons smart with a esp8266.
I want to give each button on the device a entity in home assistant, so i can control the device.
So the esp should only “emulate” buttons which are connected in parallel to the buttons on the device.

Edited after re-read…

To emulate the button press on the dumb device you may need a esp wired to each device (typically wired across the existing button terminals).

You can search for “simulate button press” on this forum or similar. You should be able to find similar examples.