Comment by lambda

You do have to set the kernel parameters once to set the max GPU allocation, I have it set to 110 GiB, and you have to set a BIOS setting to set the minimum GPU allocation, I have it set to 512 MiB. Once you've set those up, it's dynamic within those constraints, with no more reboots required.

On Windows, I think you're right, it's max 96 GiB to the GPU and it requires a reboot to change it.