I've examined the pdf metadata using Adobe Reader on macOS and the fonts used are Times (the Linotype release of Times New Roman), plus various CMM fonts for the math content. All the body text is in Times.
I wonder if your viewer on Linux is having some problems loading the fonts? Your screenshots definitely show Noto Serif (or possibly Droid Serif, which has the same Latin-alphabet characters, but no native condensed styles), perhaps being used as fallback? I don't know what pdf reader you're using but if you're on Linux I imagine it's likely an open-source pdf viewer which would very likely have open-source Noto/Droid fonts as fallback. We see here a common sign of a fallback font, condensed or stretched text caused by needing to scrunch the fallback font into a different font's metrics. That's happened here, but I'm not entirely sure why, since Times has fairly normal proportions. Maybe its vertical height is higher than Noto's or something. Anyhow, I guess the fun thing is this font is already on your computer somewhere inside the pdf program and you just need to get it out.
In the finite field pdf as I see it text in italic isn't in a real italic font, by the way, it's simply the roman slanted to the right. This is the standard action when an italic font can't be found, although I don't know exactly how this works in TeX. So there could be glitches in the pdf production.
