I tried today Lenovo T420s 16GB 240SSD, displayport>HDMI Samsung tv.
Confirmed this set up works using windows before begin.
No useful success using Linux to improve/help you solve issue.
results on tv -
Linux Lite 3.2 dvd live
Desktop part appeared on tv, sound worked.
Desktop it was wrong size and didnt show the panel or a portion of lower desktop , on tv.
Changing of resolution didn't help, only made worse in smaller sizes on tv.
Eventually I got entire wallpaper to appear on laptop and tv, but neither had a panel so had to switch off laptop to get to remove dvd.
End of trial.
Ubuntu 17.10 usb live
even less of desktop appeared in height, and also this was missing part of desktop in width on tv.
Looked at display settings, all of those tried had no visible effect at all.
Didn't try much else with it with tv.
Confirmed this set up works using windows before begin.
No useful success using Linux to improve/help you solve issue.
results on tv -
Linux Lite 3.2 dvd live
Desktop part appeared on tv, sound worked.
Desktop it was wrong size and didnt show the panel or a portion of lower desktop , on tv.
Changing of resolution didn't help, only made worse in smaller sizes on tv.
Eventually I got entire wallpaper to appear on laptop and tv, but neither had a panel so had to switch off laptop to get to remove dvd.
End of trial.
Ubuntu 17.10 usb live
even less of desktop appeared in height, and also this was missing part of desktop in width on tv.
Looked at display settings, all of those tried had no visible effect at all.
Didn't try much else with it with tv.