external monitor extremely slow with Ubuntu 20.04

I am using Ubuntu 20.04 on my laptop attached with a Dell monitor. My Nvidia driver version is 465.27 with a GeForce 3070 card. My external monitor becomes extremely slow when I close the laptop lid.

I read several posts:

Ubuntu 20.04, computer keeps shutting down when I close the lid, I've already checked logind.conf, settings are set to suspend

20.04 on external monitor (2560x1600) extremely slow

Keep Ubuntu Server running on a laptop with the lid closed?

Ubuntu graphics performance slow with external monitor AND notebook lid closed

And, I tried all the solutions but still not working. When I close the laptop lid, the external monitor still becomes very slow.

$ nvidia-smi
Fri Oct  8 13:03:13 2021       
+---------------------------------------------+
| NVIDIA-SMI 465.27       Driver Version: 465.27       CUDA Version: 11.3     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|===============================+======================+======================|
|   0  NVIDIA GeForce ...  Off  | 00000000:01:00.0  On |                  N/A |
| N/A   51C    P3    24W /  N/A |    105MiB /  7982MiB |     17%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+
                                                                               
+---------------------------------------------+
| Processes:                                                                  |
|  GPU   GI   CI        PID   Type   Process name                  GPU Memory |
|        ID   ID                                                   Usage      |
|=============================================================================|
|    0   N/A  N/A      1116      G   /usr/lib/xorg/Xorg                 34MiB |
|    0   N/A  N/A      2005      G   /usr/lib/xorg/Xorg                 69MiB |
+---------------------------------------------+

Below is my /etc/systemd/logind.conf

[Login]
#NAutoVTs=6
#ReserveVT=6
#KillUserProcesses=no
#KillOnlyUsers=
#KillExcludeUsers=root
#InhibitDelayMaxSec=5
#HandlePowerKey=poweroff
#HandleSuspendKey=suspend
#HandleHibernateKey=hibernate
HandleLidSwitch=ignore
#HandleLidSwitchExternalPower=suspend
HandleLidSwitchDocked=ignore
#PowerKeyIgnoreInhibited=no
#SuspendKeyIgnoreInhibited=no
#HibernateKeyIgnoreInhibited=no
LidSwitchIgnoreInhibited=no
#HoldoffTimeoutSec=30s
#IdleAction=ignore
#IdleActionSec=30min
#RuntimeDirectorySize=10%
#RemoveIPC=yes
#InhibitorsMax=8192
#SessionsMax=8192

Thanks in advance.

solved it by setting IgnoreLid=true in /etc/UPower/UPower.conf, thanks!

Reference: How can I tell Ubuntu to do nothing when I close my laptop lid?