But to do so, they used git head mesa3d, experimental kernel patches to get the kernel part working, and firmware blobs they took from the proprietary driver.
We'll have to wait a little more, but will get system images with all of that already working. Eventually, it'll all be upstream.
It helps that large amounts of these boards (more than every RISC-V SBC before, combined) are getting to developers. This was the whole point of the boards after all.