You don't need extensions.

There are many RSS readers with inbuilt dark theme / night mode.

Even if you prefer self-hosted RSS readers, you can find RSS readers (FOSS, not Premium/Freemium) on GitHub with such feature.

https://alternativeto.net/software/feedly/?feature=night-mod...

https://duckduckgo.com/?q=github+rss+reader+self+hosted+dark...

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rcarmo 19 hours ago | parent [-]

That does not apply to mobile apps.

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vee-kay 17 hours ago | parent [-]

You didn't bother to search.

Feeder, FeedDeck, NewsBlur, Fluent Reader, Twine, Capy Reader, Reeder, Read You, Neo Feed, Readrop are all open-source RSS/feed readers for mobile (iOS, Android, or both) , and they all have dark theme / night mode.

https://alternativeto.net/software/feedly/?license=opensourc...

https://duckduckgo.com/?q=android+ios+open-source+rss+reader...

	▲	rcarmo 9 hours ago \| parent [-]
		I don’t rate search “knowledge” as valid in this context. You clearly don’t use these or experience things in the same way.