[kleer001]

There's plenty of 3rd party solutions.

What have you already tried and why don't they work for you?

[bananamerica]

On mobile?

hi, downvoter... it was an honest question. Sorry? :(

[dbjorge]

On Android I use an app called Materialistic, which has a dark mode

[cubedrone]

I use a firefox mobile add-on called 'night mode - hacker news'

[bananamerica]

This[1] and other links tell me that there are no addons for Firefox on iOS. Sadly, that is what I use.

[1] https://support.mozilla.org/en-US/kb/add-ons-firefox-ios

[kick]

Firefox for iOS has night mode built in.