It took me ages to find this link, I don't want to lose it.

https://forums.developer.nvidia.com/t/enabling-resizable-bar-on-rtx-30-series-gpus-in-linux/239950

There will be notes.

Maybe.

There are absolutely no notes.

After dickin' about for ages to get the firmware flash tool and everything ... I just had to enable the setting in my BIOS.

yup.

Check yo' BIOS first, folks.