Is NVIDIA-on-NVIDIA PRIME supported?

I have a PC with a GTX 1080 and a RTX 2080 TI. I’m using the GTX as main card for day-to-day usage, I would like to set up PRIME rendering to offload heavy games onto the RTX, like one might do with a integrated Intel/NVIDIA setup.

I have tried doing so a couple releases ago and I wasn’t able to. I don’t remember the specifics, perhaps it was because I couldn’t set the GTX as offload sink with xrandr, and also because I had to tweak the driver configuration to leave the RTX alone to be used with xrandr in the first place.

Is it unsupported, is it planned, or do I just have to spend more time on this? The last driver release mentioned reverse PRIME so it might be possible now in theory…