Starting at left is a ESP32 Breakout board, then one of my own STM32F405RG breakout boards, a 5″ HDMI, Wireless keyboard and Raspberry PI 3 with my 5 port Hat – and your right it’s a different Hat with screw terminals, so I do have 2 x 5 port Hat’s working.
What I will do here is to wire up SPI between ESP32 & STM32 for testing, and I can add CAN breakout boards etc getting the boards to communicate. The only drawback here is that I can only use one SWD at the time, but I will get around that.