So, I was trying to figure out how to get 4.1 on my Ubuntu 16.04 machine a few days ago and could never figure out how to get it. Here is my source list, I don't remember where I got this from:
deb TVHEADENDMIGRATIONSTART2855d05d34854d6fa6f4d97819c1d83dTVHEADENDMIGRATIONEND xenial main
From TVHeadend site I found this the other day:
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 379CE192D401AB61
echo "deb TVHEADENDMIGRATIONSTART4a9c5a11df6742f592d3571a7b3f0451TVHEADENDMIGRATIONEND xenial release" | sudo tee -a /etc/apt/sources.list
However, if I remember correctly while testing on a VM I attempted to use the "unstable" and never received 4.1.
Which source are you using?
And finally, @George Kazaroth, I want to truly thank you for your quick responses and assisting me on this thread. You have been incredibly helpful.
After all is completed and working for me I plan on documenting all these steps and posting to my blog for my own future reference and for anyone else looking to do what I am doing with an OTA antenna and PVR on an Ubuntu server.