I think there is another project doing RISC-V GPU: https://www.pixilica.com/graphics

Also the latest announced RVB-ICE should have a OpenGL ES 3+ capable Vivante GC8000UL GPU (did not manage to find documentation for this exact version but all GC8000 seem to): https://www.aliexpress.com/item/1005003395978459.html

Disclaimer: Expensive if you don't know if it's vapourware and how the drivers and linux works!