No proprietary drivers are in use + "ubuntu-drivers list" no output

I have installed Mate 20.04 but the Software & Updates > Ubuntu software > Proprietary drivers| option does not display anything.
Below I see " no proprietary drivers are in use", but I have installed the Nvidia drivers and others !!.
I have made sudo apt update. All OK but no result.
I have linked the repository and Canonical Partner. I made the reload. Nothing.
If I type $ ubuntu-drivers devices or $ ubuntu-drivers list , not display anything.
Perhaps there is a problem in the security settings loaded when the system boots ?
[ 20.04.1 LTS (Focal Fossa) 64-bit - Kernel Linux 5.4.0-56-generic x86_64 -- Graphic: llvmpipe (LLVM 10.0.0, 128 bits) -- Nvidia Geforce 6200 ]
Please help !

can you post the output of inxi -F

Here it is the inxi -F output
System: Host: gianfranco- Kernel: 5.4.0-56-generic x86_64 bits: 64
Desktop: MATE 1.24.0 Distro: Ubuntu 20.04.1 LTS (Focal Fossa)
Machine: Type: Desktop Mobo: ASUSTeK model: P5P800 v: Rev 1.xx
serial: <superuser/root required> BIOS: American Megatrends v: 1011.001
date: 06/28/2005
CPU: Topology: Single Core model: Intel Pentium 4 bits: 64 type: MT L2 cache: 2048 KiB
Speed: 2800 MHz min/max: 2800/3200 MHz Core speeds (MHz): 1: 2800 2: 2800
Graphics: Device-1: NVIDIA NV44A [GeForce 6200] driver: N/A
Display: x11 server: X.Org 1.20.8 driver: fbdev,nouveau unloaded: modesetting,vesa
resolution: 1024x768~76Hz
OpenGL: renderer: llvmpipe (LLVM 10.0.0 128 bits) v: 3.3 Mesa 20.0.8
Audio: Device-1: Intel 82801EB/ER AC97 Audio driver: snd_intel8x0
Sound Server: ALSA v: k5.4.0-56-generic
Network: Device-1: Marvell 88E8001 Gigabit Ethernet driver: skge
IF: enp2s5 state: up speed: 1000 Mbps duplex: full mac: 00:13:d4:9e:e2:d2
Drives: Local Storage: total: 260.84 GiB used: 10.66 GiB (4.1%)
ID-1: /dev/sda vendor: Western Digital model: WD1600AAJB-00J3A0 size: 149.05 GiB
ID-2: /dev/sdb model: SATA3 120GB SSD size: 111.79 GiB
Partition: ID-1: / size: 27.62 GiB used: 10.66 GiB (38.6%) fs: ext4 dev: /dev/sda5
Sensors: Message: No sensors data was found. Is sensors configured?
Info: Processes: 188 Uptime: 3h 47m Memory: 3.60 GiB used: 1.80 GiB (50.1%) Shell: bash
inxi: 3.0.38

This shows you have a Nvidia card but the driver is nouveau.

if you type, ubuntu-drivers devices do you get a list of available drivers?

sudo ubuntu-drivers autoinstall should install what's appropriate for your h/w.

this link may help...

Thank you for the quick replay.
With $ ubuntu-drivers autoinstall i receive : No drivers found for installation.
I Have installed the last driver that supported NVIDIA Geforce 6200 (NVIDIA-Linux-x86_64.304.125) but I don't see it in Software &Updates>proprietary drivers. So I installed it by hand but, just at the end it says like "not succeed in rebuilt kernel".
But I don't understand why the ubuntu-drivers list command gave no output.

Maybe you need to uninstall the nvidia driver (purge everything nvidia) and start again.

I don't know how you installed your driver, it should be listed. The DKMS module could not be built. So, start from the beginning and hopefully you will have success.