NVIDIA-SMI failed to communicate with the NVIDIA driver

Hi there,
I have installed ubuntu 18.04 (kernel 5.4.0-77-generic) in a lenovo YangtianM4000q-11 PC with a intel Core i7-10700 processor, and an NVIDIA GK208B [GeForce GT 730] card.

I knew that I should use a legacy driver so I choose nvidia-driver-390 in Software & Updates. However, nothing changes after reboot. With inxi -G, the outputs were

Graphics:  Card: NVIDIA GK208B [GeForce GT 730]
           Display Server: x11 (X.Org 1.20.8 )
           drivers: fbdev,nouveau (unloaded: modesetting,vesa)
           Resolution: 1920x1080@77.00hz
           OpenGL: renderer: llvmpipe (LLVM 10.0.0, 256 bits)
           version: 3.3 Mesa 20.0.8

And with nvidia-smi, the output was

*NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.*

nvidia-bug-report.log.gz (94.5 KB)

Btw, in /etc/default/grub, I set GRUB_CMDLINE_LINUX=“acpi=off nomodeset”, I wonder if its’ the cause that the driver cannot connect to the GPU.

However, if I remove “acpi=off”, the ubuntu system cannot boot with the error “AE_ALREADY_EXISTS”… and “critical temperature reached (186C), shutting down.”

Really need your help!!!