GNU/Linux Debian Bullseye Installing NVIDIA GeForce RTX 4080 Driver Guide
Hi! The Tutorial shows you Step-by-Step How to Install NVIDIA GeForce RTX 4080 Graphics and GPU Driver in Debian Bullseye 11.x Desktop.
The NVIDIA RTX 4080 Debian 11 Driver Setup is Simple and involves just the execution of a few Basic Shell Commands.
Especially relevant: currently the NVIDIA 525+ Driver is not available in the Debian 11 Repos.
So here I propose as an available Solution the latest Generic Linux Driver build from NVIDIA.
Again in case of Installation Issue you should priorly see the Upgrade Kernel Guide.

GNU/Linux Debian 11 GeForce RTX 4080 Driver Installation Guide