I get the same result: zero gpus. I guess the library does not detect it.
This is the output of the command line tool nvidia-smi before and after loading shadertoy:
a@b ~> nvidia-smi
Mon Dec 2 14:23:27 2019
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 418.56 Driver Version: 418.56 CUDA Version: 10.1 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 1060 Off | 00000000:01:00.0 On | N/A |
| N/A 53C P0 27W / N/A | 353MiB / 6077MiB | 0% Default |
+-------------------------------+----------------------+----------------------+
+-----------------------------------------------------------------------------+
| Processes: GPU Memory |
| GPU PID Type Process name Usage |
|=============================================================================|
| 0 1246 G /usr/lib/xorg/Xorg 18MiB |
| 0 1280 G /usr/bin/gnome-shell 48MiB |
| 0 2189 G /usr/lib/xorg/Xorg 102MiB |
| 0 2333 G /usr/bin/gnome-shell 181MiB |
+-----------------------------------------------------------------------------+
a@b ~> nvidia-smi
Mon Dec 2 14:24:35 2019
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 418.56 Driver Version: 418.56 CUDA Version: 10.1 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 1060 Off | 00000000:01:00.0 On | N/A |
| N/A 57C P0 46W / N/A | 549MiB / 6077MiB | 25% Default |
+-------------------------------+----------------------+----------------------+
+-----------------------------------------------------------------------------+
| Processes: GPU Memory |
| GPU PID Type Process name Usage |
|=============================================================================|
| 0 1246 G /usr/lib/xorg/Xorg 18MiB |
| 0 1280 G /usr/bin/gnome-shell 48MiB |
| 0 2189 G /usr/lib/xorg/Xorg 103MiB |
| 0 2333 G /usr/bin/gnome-shell 186MiB |
| 0 12806 G /usr/lib/firefox/firefox 189MiB |
+-----------------------------------------------------------------------------+
It shows power consumption, ram and GPU usage.