I am currently running Debian 12 with Gnome using the 6.6.9-amd64 kernel, and have had quite the issues with the newer kernels. Once i switch to them in the grub menu, I am only able to use a single monitor which has been set to a sub-normal resolution. Also animations for the DE are all gone. I can’t add my other monitors in, my nvidia settings panel lost most of its settings (from about 20 tabs to 3) and the entire system runs really poorly. While part of this seems to be an nvidia thing, I do wonder how I would actually go about fixing this.
You want to run a stable debian kernel, not “bleeding edge” stuff from the backports repo. It’s likely that your NVIDIA drivers are not compatible with the more modern kernel, either for real reasons (they’re old) or because that’s how they were packaged.