Se precisa executar os códigos exemplos cuda sem privilégio de root, e o comportamento é similar a retorno abaixo, deixo neste post como contornar o problema:

$ optirun ./deviceQuery
./deviceQuery Starting...
 CUDA Device Query (Runtime API) version (CUDART static linking)
cudaGetDeviceCount returned 999
-> unknown error
Result = FAIL

Basta executar o comando na linha de comando e pronto!

$ modprobe --force-modversion nvidia-uvm

Em seguida, execute o exemplo novamente.

$ optirun ./deviceQuery
./deviceQuery Starting...
 CUDA Device Query (Runtime API) version (CUDART static linking)
Detected 1 CUDA Capable device(s)
Device 0: "GeForce GTX 1660 Ti"
  CUDA Driver Version / Runtime Version          11.0 / 10.2
  CUDA Capability Major/Minor version number:    7.5
  Total amount of global memory:                 5945 MBytes (6233391104 bytes)
  (24) Multiprocessors, ( 64) CUDA Cores/MP:     1536 CUDA Cores
  GPU Max Clock rate:                            1590 MHz (1.59 GHz)
  Memory Clock rate:                             6001 Mhz
  Memory Bus Width:                              192-bit
  L2 Cache Size:                                 1572864 bytes
  Maximum Texture Dimension Size (x,y,z)         1D=(131072), 2D=(131072, 65536), 3D=(16384, 16384, 16384)
  Maximum Layered 1D Texture Size, (num) layers  1D=(32768), 2048 layers
  Maximum Layered 2D Texture Size, (num) layers  2D=(32768, 32768), 2048 layers
  Total amount of constant memory:               65536 bytes
  Total amount of shared memory per block:       49152 bytes
  Total number of registers available per block: 65536
  Warp size:                                     32
  Maximum number of threads per multiprocessor:  1024
  Maximum number of threads per block:           1024
  Max dimension size of a thread block (x,y,z): (1024, 1024, 64)
  Max dimension size of a grid size    (x,y,z): (2147483647, 65535, 65535)
  Maximum memory pitch:                          2147483647 bytes
  Texture alignment:                             512 bytes
  Concurrent copy and kernel execution:          Yes with 3 copy engine(s)
  Run time limit on kernels:                     Yes
  Integrated GPU sharing Host Memory:            No
  Support host page-locked memory mapping:       Yes
  Alignment requirement for Surfaces:            Yes
  Device has ECC support:                        Disabled
  Device supports Unified Addressing (UVA):      Yes
  Device supports Compute Preemption:            Yes
  Supports Cooperative Kernel Launch:            Yes
  Supports MultiDevice Co-op Kernel Launch:      Yes
  Device PCI Domain ID / Bus ID / location ID:   0 / 1 / 0
  Compute Mode:
     

deviceQuery, CUDA Driver = CUDART, CUDA Driver Version = 11.0, CUDA Runtime Version = 10.2, NumDevs = 1
Result = PASS