Used to have one on Streamtvbox that was a direct feed from NFL Game Pass, been using Flawless and whilst I like the service and their fight coverage was perfect, NFL Network and ESPN barely ever work properly, and when they do the channel is often changed to SEC Network (NFL Network) or ESPN Mexico (ESPN), their response was "well that's just our supplier" and to deal with it basically. Want to a find a better provider for the new season. Need Sky Sports and BT Sport too, so Torula is out of the question atm.
I know Smoothstreams provides stable and unchanged feeds of all ESPN channels (except ESPN 3, the streaming service, but they do add some ESPN3 feeds recently for US Open, but they are temporary). They also have NFL Network channel, not sure if it is fixed or not (SS often switch feeds for live events), but I think they will not touch it since it is also sports channel. They recently add 24/7 sky sports and bt sports it seems.