The Raspberry Pi line is full of capable compact computers, but they’ve never been the strongest in the bunch when it comes to graphical output. Nor have they been particularly expandable in that regard. However, that’s all beginning to change, with Jeff Geerling reporting success getting external GPUs to work on the Raspberry Pi 5.
This is really early days to demonstrate what is possible (seems Nvidia may still be a problem). So, it’s not ready yet for a copy-and-paste for everyone to use, but all the efforts have been open sourced for others to follow and contribute to.
See https://hackaday.com/2023/11/30/the-raspberry-pi-5-can-use-external-graphics-cards-now/