While having an online meeting on platforms like Skype, Google Meet, and Zoom, whenever we share our screens it always shows as a black screen with a mouse cursor to other people in the meeting. This is a standard problem with Ubuntu PCs.
To fix this problem, open the following file:

/etc/gdm3/custom.conf

And then simply uncomment following line:

#WaylandEnable=false

Now restart your system and enjoy sharing your screens in online meetings without having a black screen and a mouse cursor!