UEFI Secure Boot root cause

openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -out MOK.der -nodes -days 36500 -subj "/CN=VMware/"
sudo /usr/src/linux-headers-`uname -r`/scripts/sign-file sha256 ./MOK.priv ./MOK.der $(modinfo -n vmmon)
sudo /usr/src/linux-headers-`uname -r`/scripts/sign-file sha256 ./MOK.priv ./MOK.der $(modinfo -n vmnet)
mokutil --import MOK.der
sudo systemctl reboot

1. "Cannot open /dev/vmmon: No such file or directory" error when powering on a VM (2146460)

First of all, you are make sure installed open-vm-tools-desktop first.

sudo apt install open-vm-tools-desktop

If open-vm-tools-desktop already installed.

You should check Virtual Machine Setting Stretch Mode is disabled . This feature must be disabled!!

Hardware -> Display
Display Extension
Stretch Mode must be disabled