Downton Abbey feature film

I have not seen the film , so I can't comment on it. But the Downton Abbey of the past is a unrealistic version of the life in a large British family house ,set in early twentieth century .There are some references to actual events of the time , the sinking of the Titanic was one . It's made to be popular entertainment and it has been popular. I'm sure the film will not require any previous knowledge.

Hmm, I think you might struggle, tbh. I took my parents to see it last week and, even though they'd followed the TV series, they spent the first 20 minutes or so trying to work out relationships or remember where things had left off. I'd previously watched the TV shows too, but I'd also binge-watched them again recently so I was pretty much up to speed on it.

The plot itself is stand-alone, but you might be scratching your head at some interactions/exchanges as you're not familiar with the characters and their personal history.

I heard a review of the film on Welsh-language radio, and the critic said you can enjoy it without having seen the series, but you will enjoy it MORE having some familiarity with the show. No spoiler here, but she said the movie is more visually appealing than it is substantively strong.

I'd suggest watching the feature first, then, if you decide to watch the series, you will watch things develop to an end point, with many cries of "Aha!"
If you try to binge watch all those seasons at once, you will likely be either burned out, or desperately trying to remember all the stuff that you just pumped into your brain, without time for it to settle.

It's definitely worth watching for all those reasons you mention, Arden, and is a delightful, heart-warming way to spend a couple of hours. I can give you the low-down on a few of the more pertinent characters/strands to the plot prior to the film taking place, if you don't have time to binge-watch if you decide to go?

My oldest son and I watched and loved the series. We went to the movie along with my youngest son, who had never seen an episode. While I am sure first son and I got more out of it, second son loved the movie as its own standalone story. He quickly understood the characters and just enjoyed the story it presented. It was nice to see him cheering on a certain character I had always loved lol. I look at it this way - most movies you see you take as a snapshot in time, without years of backstory. Same here. Take the story for what it is and if you are interested, look at the series as a bunch of prequels. Second son now plans to binge watch the series!