The current beta build of AnkiMobile introduced a glitch that makes the UI font inconsistent; characters are still written in a sans-serif font, while digits are now written in a serif font instead. This issue might be exclusive to Chinese, I haven’t tested other languages.
Of course the text is still readable, it’s just a bad stylistic choice.
I’m attaching screenshots that compare this build with the previous one. They show the screen where it tells you that your current reviews are done, but there are some reviews coming up later in the day.