On the 3rd episode of Deutschland 83...very good if you don't mind subtitles.
Tried it. Made it about as far as you have . . . and my interest faded. Hope it works out better for you.
And . . . I watched Tenet. The package I bought on The Bay was all original and excellent for about ten bucks . . . Blu ray, DVD and digital copy.
Thoughts (spoiler free, I think) . . .
I liked (didn't love) it. I didn't find it hard to follow as many folks mentioned, but I can see why that would be the case for many. I'm guessing there was a lot left on the editing room floor . . . maybe an even longer "Director's Cut" that would fill in some of the gaps in the plot will come out at some point.
I thought it was very well acted. Parts of it reminded me of a James Bond movie, and I even wondered how it might have been if they were able to make The Protagonist be . . . 007. I'm a big Bond fan, so I really liked those aspects of the movie.
The plot required a LOT of "leaps of faith" which you just have to accept, as Christopher Nolan's movies often do. A lot more such leaps than even "Inception." My main criticism would be that Nolan seemed more interested in showing off and exploring movie-making tricks than in plain old-fashioned storytelling. I'm sure that was very interesting for him . . . not necessarily so much for the viewer. In fact, I think he just made this movie for himself - not for any particular audience. Watching it requires an investment . . . it's not what I would call "a popcorn flick" and I definitely don't think it's for everybody. I think that folks who are interested in the art and craft of movies are probably going to enjoy it more than folks just looking for a couple of hours of diversionary entertainment, or a good old-fashioned story.
Last remark . . . I would be curious if anyone else who watched this, and Inception, and The Prestige noticed similarities in the way Nolan filmed and edited the climactic scenes in all of these movies. Time and timing seem to be a big thing for him.
