If you're not okay with extensions then use Opera which has night mode as a built in feature and for God's sake today only I noticed it very good to use than other dark modes which I used in the past to filter blue and not harming my eyes. Dark mode in Opera is giving good details than others and also you have settings to dim the brightness of the keyboard as well in case if you're a mobile user.
That's it for now and I will add more if I found anything interesting.
P.S I am writting this in dark mode on Opera browser.
For Android mobile users there are a few browsers that enables chromium extension. Opera does work fine but it is slow and heavy. A few days back I came across an Android browser known as Lemur. Doesn't require a lot to understand it as it is similar to the others. Does come up with ChatGPT3 as their own buit in browser extension. Dark mode is when enabled doesn't work for the forum. There are extension for it.
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https://bitcointalk.org/index.php?topic=4423230.0Not sure if it is still available!