https://thenextweb.com/apps/2019/09/25/instagram-is-reportedly-testing-dark-mode-heres-what-it-looks-like/

We’re officially in the dark mode era. iOS 13 and Android 10, which rolled out recently, both have that option. Sadly, not all appsautomatically respond to the dark theme on your phone and turn the lights down.

However, according to reports by Android Police and 9to5Google, Instagram is testing a dark mode that not only works on Android 10, but on some of previous versions too.