All Replies (3)
Here is a link to an earlier thread on this. I'm not sure whether there are any updated options since April: How can I turn on the night mode in the browser?
It works on luminosity, it activates when you're in a dark room or under low light conditions. You can also manually set this by tapping the 'Aa' icon in reader mode and setting this to Dark/Light/Auto.
How is reader mode set as default?