I also had some difficulty getting it working on my rig, and I’m not a big fan if Debian’s documentation, as it often does assume knowledge, which makes it harder to follow along and feel confident you’re doing the correct steps.

Ultimately I switched my only Nvidia system to standard Linux Mint to have access to their easy to use Nvidia driver installer, which makes upgrading or downgrading the driver a 1-click process (though it requires a third party PPA done by a canonical employee to access the latest 610 drivers).