CUDA install removes Nvidia driver in ubuntu 18.04

After installing CUDA 11, It removed my Nvidia driver.

$nvidia-smi
NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

$nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2020 NVIDIA Corporation
Built on Wed_Jul_22_19:09:09_PDT_2020
Cuda compilation tools, release 11.0, V11.0.221
Build cuda_11.0_bu.TC445_37.28845127_0

$uname -r
5.4.0-47-generic

It doesn’t allow me to select Nvidia from the software & updates center. Why is that?

Should I install my Nvidia driver manually? Because previously I had an issue with the black screen after installing manually the Nvidia driver. I need your suggestion. What should I do?

Looks like, CUDA 11 is incompatible with Nvidia 340.108, and that’s why when I install CUDA, It installed nvidia-driver-450 and removed nvidia 340.108.

Tue Sep 22 11:52:40 2020       
+------------------------------------------------------+                       
| NVIDIA-SMI 340.108    Driver Version: 340.108        |                       
|-------------------------------+----------------------+----------------------+
| 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 820M        Off  | 0000:03:00.0     N/A |                  N/A |
| N/A   49C    P0    N/A /  N/A |    212MiB /  2047MiB |     N/A      Default |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Compute processes:                                               GPU Memory |
|  GPU       PID  Process name                                     Usage      |
|=============================================================================|
|    0            Not Supported                                               |
+-----------------------------------------------------------------------------+

Although sudo ubuntu-drivers autoinstall install nvidia-driver-450 but nvidia-smi show NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

Installing nvidia-driver-390 looks like compatible.

+-----------------------------------------------------------------------------+
| NVIDIA-SMI 390.138                Driver Version: 390.138                   |
|-------------------------------+----------------------+----------------------+
| 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 GT 820M     Off  | 00000000:03:00.0 N/A |                  N/A |
| N/A   55C    P0    N/A /  N/A |    214MiB /  1985MiB |     N/A      Default |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|    0                    Not Supported                                       |

Now Which Cuda toolkit is compatible with the above driver?