It’s possible to pass through the GPU to a container. But is there a way to actually allow the container to take over the framebuffer?
After the TrueNAS is booted, what’s displayed on the console is essentially useless. To have an LXC with a GUI e.g. lightweight XFCE, from which to run a variety of things, would make life considerably more convenient…
A much less palatable option is to maybe run X11/xrdp on some virtual screen, and connect with RDP to the system, but that’s a lot more fragile.