linux rdp show screen different users

I need software that can run on Linux as a server and share the current user's screen with a remote viewer.

I have tried these softwares but they start a new session:

xtighvncviewer

remmina

Tightvncserver on Windows works when the user's screen is shared, on Linux it opens a new session for the remote user.

Do I do something wrong with config?

Are there alternatives?