This project using $8 in electronic parts, utilizes the ultra tiny Seeed stuido XIAO ESP32C3 board. There are cheaper boards using the new budget ESP32 model, the ESP32C3. (This single processor board is functionally close to it’s predecessor the ESP8266, the new chip uses an open source Risk-V processor, saving a little license cost.
(I got a few of the Seeed stuido XIAO ESP32C3 boards in 4 days from Digikey.com for $4.99 ea.
The how-to Video https://www.youtube.com/watch?v=t3CMiI9x7L8
His whole rack appears be homebrew modules, the How-to page is in Japanese.
You can see some 0.96" OLED displays, my other recent post shows an ESP32-C3 with a built in 0.42" display