Have a look at http://www.mythtv.org for an excellent introduction for mythtv.
I have been using mythtv for several years now, and I learned that installation (apart from the software itself) and maintenance are not trivial. The wiki gives detailed instructions. If you want to run mythtv: read the instructions carefully before doing anything.
The installation of the software itself is trivial on Ubuntu:
sudo apt install mythtv.
I installed mythtv, living in the Netherlands and using Ziggo as provider. Fortunately, Ziggo now delivers the free channels ("Kabel-TV") also in digital (DVB-C).