Your best bet to get help would be to post this on the arduino forum in this section:
There is a user, david_prentice, that frequents that area often and is very knowledgeable when it comes to displays. You mentioned the mcukvb library. When I google for that, I get results for the mcufriend_kvb library and he’s the guy who wrote that library. If you post there, include a wiring diagram and a link to a data sheet or information about the display.
I’m thinking you have all the connections you need on the “con1” connector that you will need to run the display. I’m curious as to why you want to run in 8 bit mode. Using SPI, and fewer connections, on an ESP32 with a 2.8 display like this works really well, really well.
While looking to get a link to the display I use, I came across the display you are using here:
I don’t see why it wouldn’t work using “con1”, if it works while using the UNO pins instead. So, how do you have it wired up?