I have a Kogan KALED55KU8000SZA 55-inch Smart TV - identified by My Device Pro as an "MStar Android TV" from "MStar Semiconductor", using the "arbutus" board and the "monet" hardware. It runs Android TV 5.1.1 ("Lollipop"), Build aosp_arbutus-userdebug 5.1.1 LMY47V 1.1.20170720.153235 test-keys.
I've asked elsewhere on this site about replacing Android TV with another Linux-based operating system (such as Ubuntu), however as I expected, it's looking like this might not be a realistic solution... So now I would like to "root" this "smart" television, in order to remove some of the rubbish which is included and set the "smart" television to either switch to HDMI "x" when I turn it on or automatically run Kodi/XBMC for Android when I turn the "smart" television on.
Courtesy of Xda Developers, I have thus far tried:
* -Key Root Master (MOD Version) 1.3.6, which crashes when I try to run the application;
* KingRoot 5.3.7, which does not seem to work (it counts up to 25% on the "Aquiring Root" screen, then tells me that "root failed");
* Framaroot 1.9.3, which tells me Your device seems not vulnerable to exploit included in Framaroot.
I can see that KingRoot supposedly has more "root" success via USB debugging, but I cannot seem to get the "developer" mode to appear because when I do the "click on build seven times" thing, nothing happens and no extra menus appear... The "smart" television has multiple USB ports and wireless (Wi-Fi) connectivity; I'd need to physically check but (Android) settings seems to think it has an ethernet port too,
Has anyone has any luck "rooting" these "smart" televisions?

If the developers on XDA steered you to Kingroot and Framaroot, it means that none of them have found an exploit that will boot the device into temporary rooted status. Evidently neither have the developers at Kingroot or Framaroot (all those programs do is send device information back to the server, so the server can send the right program that can root the device).
So evidently no one has ever found an exploit that works on that device (because no one has worked on it, probably). Each device, with each version of Android, needs a different exploit found for it. (And most manufacturers, as soon as an exploit is found, patch it om the next update, so another method has to be found.)
If the device uses an ARM processor, you might try Magisk Releases· GitHub - you'll need both the binary and the manager. (If the manager app doesn't download and install the binary, you can install TWRP [if there's a version that will run on that device] and install it manually.)

The truth is there’s no need to root to remove unwanted software, because it is a “userdebug” build, you have a full root access through adb, if you’re interested i can give you commands to list installed packages and then remove desired package..
I saw almost all your post request on many different website, and i believe to have the same 55” tv, but Philips’s branded.. the rom for the philips starts the tv on the last selected input (in my case it’s almost always the hdmi 1 with a mibox connected on it). Are you still interested to try to improve this device ? (I personally gave up as it’s seems we are 3 to really have interest in it..)
I managed to get working google playstore app& services, but i deactivated them as i’m still unable to get a bluetooth dongle working with this device (even if all drivers are presented in this system.. i want to get the tv connected to a bluetooth speaker.. boring..)
Ho, can you share some screenshot of the UI kogan offers ? The philips one is really sad.. another question is, does kodi works well on it ? All kodi build i tried (17 to 18) were unable to read a 1080p mkv properly, whereas vlc was..