Ubuntu 18.04 Top Panel only on one monitor
Check out the Gnome Shell Extension Multi Monitors Add-On.
Just to mention it: A previous version of this post referenced to the Multiple Monitor Panels Extension, which isn't working properly in 18.04.
In Ubuntu 18.04 there is an inbuilt setting for replicating Doc (EDIT: this answer dosen't answer the asked questions but would like to help people in replicating doc for multiple monitors so just kept it here):
Open Settings >> Dock >> Show on: All Displays
Done :)
In Ubuntu 18.04, go to "Settings", "Devices", "Screen Display". Click on "Primary Display". Choose the display you want the top panel to appear. After doing this, you may need to re-adjust where the dock is positioned using "Settings", "Dock".
i had the same problem and solution for me was:
- open : open setings>>Apperance and in option Show on: first change all displays it shows top bar and activities bar on all monitors and then switch to Built-in display(Primary Display) that switch all on built-in display.