free TV is thru m3u playlist files ...a simple rich text doc is all the file is, which is an address to an online source of the playlist , which may be one channel or a few , which may be active and current or which may be dead.
Them m3u playlists are never a consistent source for enjoyable TV watching.
Most any android box if not all android boxes are m3u compatible. All the above boxes you mentioned are.
Now one step better then m3u playlists are applications created by developers which include lots of content and are found online given volentarly by the developer, and for most part are free.
You would run these apps thru a Kodi platform or system, so to speak.
The Kodi OS can be installed on all them boxes you mentioned as well (except the Mag boxes).
With the AVov and Mag 250 and 254 and with the Dreamlink T1, they all can run a private server thru their onboard functions and ability. With all other boxes you woud run a private server thru an app which would in turn run thru the Kodi system, which you would have already installed on your android box.
So the AVov and Mag and T1 have an advantage in that way as they do not need the extra Kodi app.
There are other things to consider too, The Mag receivers do not have the ability to run Kodi but can run a private server with their own onboard functions.
While the Dreamlink T1 and Avovs can run Kodi and also the private stuff without Kodi.
The Dreamlibk T6 can run IKS and IPTV and Kodi.
The T6 must run private server thru Kodi thou. The T6 is good receiver but can be glitchy for the expense
The Dreamlink T1 is strickly android with no IKS (fta) ability
Kodi is a source of abundant content , you need to remember.
So having Kodi is a great big plus even if you do not need it.
The other androids can all run Kodi as well, and some of them more expensive models have the power to back up the expense.