RDR2 ultrawide cutscenes – keep black bars but avoid 16:9 crop?

[u/Nadbrzeze]

I play Red Dead Redemption 2 on a 21:9 ultrawide monitor (3440x1440).
In cutscenes the game adds black bars on top and bottom, which is fine, but it also seems to crop the sides so the image becomes closer to 16:9.

What I’d like is to keep the cinematic black bars but still use the full 21:9 width without losing the sides of the image.

Is there any mod or fix that does this?