euler-digitsoption. Unfortunately, with the
\setmathfontalso the digits within the DOI identifiers in my bibliography are changed, and thus look really ugly. I tried using and explicit
\setmonofont, that does change the letters and symbols, but still not the digits, whether I set the mono-spaced font before the math font or after it. Also note I only set the FreeMono as mono-spaced font for extra contrast to see what changed, I think it's rather ugly and definitely prefer a font better fitting with the rest of the text.
Below are the files "test2.tex", and "test2.bib" (sorry, "test.tex" was already actively in use ) I also attached the corresponding output on my system.