Google chrome remote desktop connection only display wallpaper

There is no solution, since there is no problem.
Chrome Remote Desktop (as a default behaviour) does not allow you to control the ongoing session.
Instead, it creates another virtual session on tty20, as explained in the reference.

By default, the system will create a virtual desktop that is 1600x1200 pixels in size.

It is something completely different from, say, Teamviewer, because it does not allow you to manipulate an open session.
Instead, it creates a new one.
The first time that I saw it I was surprised to, and I ended up uninstalling it ;)

Googling a bit I found that there is a workaround to modifiy this behaviour, this.
I just want to point out and stress that this is not the way it is intended to work, so it might end up breaking something.