How to enable desktop sharing?

According to feature matrix the free jitsi supports desktop sharing.

In web browser no sharing option is available.

Jitsi desktop is uninstallable

WTF?

What browser are you trying with?
When you load a meeting in meet.jit.si, do you see a “Share your screen” icon in the form of a monitor on your lower left corner?
Jitsi desktop is another type of software. If you want to use Jitsi Meet conferences from the desktop, you can try jitsi-meet-electron instead: