I've never ever watched this show

You'd probably need to watch the show for context

It's the same premise as Upstairs Downstairs, but with a ridiculous amount of friendly equality between the toffs and their peasants, which just didn't happen in real life. It's a fantasy of everyone making nice between the classes.

I actually moderately enjoyed the show and watched it. But despite that, I find myself having totally zero interest in the movie. Don't know why, just all Downtoned out I guess. It's been four years and I don't care anymore.

I do think you'd have to see the show to get the "lay of the land" of the characters and relationships of the movie, yes.

I also have never seen this show, Foebane, but I do enjoy turning up my collars and asking strangers in a British accent if they've seen the latest series of Downtin Abbey on the tele.

DON'T watch the movie until you have watched the show. Just don't.

Not because of the movie, but because of the show. The show is really well written, one of the best written shows in the last two decades. It's a bloody masterpiece. The day you start watching it, you wanna do it without spoilers.

And there's gonna be a lot of spoilers in the movie, since the movie continues the story.

So, watch the show, and then watch the movie. This way you will enjoy the show without spoilers, and you will enjoy the movie much more.