I just saw a clip about this movie earlier today. It has limited run showings in the US today and again on December 27 before opening a bid more widely in mid- January. I doubt it will ever be seen in a great number of theaters.
The Director Peter Jackson was given access to the British War Museum archives to over 600 hours of film from World War I. Using modern technology they cleaned up and colorized these grainy black and white films. They also used lip readers to add voices where they could. They also used stories from the actual survivors from the "Great War" that had been recorded about 50 years ago to add context. The results are amazing.
We are not able to go today but will try and get tickets for a showing on the 27th.
https://www.youtube.com/watch?v=IrabKK9Bhds