I had a similar issue with ubuntu 18.04 kernel 4.15.
As I undestand :
- Since nvidia-smi doesn’t reply an error message, your driver are seemingly properly installed and in use.
- “No devices found” was in my case a problem related to nouveau driver
I set the nouveau mode 0 and updated grub (beware that the “/etc/” line has not been sufficient in my case. The “/lib/” one was also necessary.
echo options nouveau modeset=0 | sudo tee -a /etc/modprobe.d/nouveau-kms.conf
echo options nouveau modeset=0 | sudo tee -a /lib/modprobe.d/nouveau-kms.conf
sudo update-initramfs -u
This solved my issue.