Hey, Vanessa,
It's good to know the cabin-sized models are never totally upright. They are so small, and such a type of frame that would allow an upright seating just doesn't work well with that compact design. From my point of view, the most upright buggy in that category would be the Joolz Aer+, and even that one isn't a totally 90-degree seat. Also good to know is that its't not just about the backrest angle, but also about the overall design and the depth of the sitting area.
Check the Kinderraft Nubi 2 as well, and I was reasonably alright with how the seat back is on the Chicco Goody.
From the larger options, the reversible models like the Joie Versatrax, Cybex Talos, and similar will be more upright. The rule is - reversible strollers are usually more upright, and the lighter you go, the less upright the seat will be, usually. The best is always to try it in real life, as it also differs from child to child (as the sitting habits differ).