Something doesn't smell right here. IANAL, but my understanding as someone who's read the entire text of the GDPR is that it regulates personally identifiable d

Something doesn't smell right here. IANAL, but my understanding as someone who's read the entire text of the GDPR is that it regulates personally identifiable data, not cookies/local storage. The OP seems to be conflating the GDPR with §25(1) of the German Telemedia act, and it does indeed have a prohibition against using local storage. But it also says that local storage is allowed if it "is absolutely necessary so that the provider of a telemedia service can provide a telemedia service expressly requested by the user." (machine translated) So it's not the GDPR that's at issue, it's a particular German law, and that law appears to have a carve-out that specifically applies to the feature under discussion. Dark mode is a service that's (presumably) expressly requested by the user. Contact your own lawyer if you're concerned, but this seems like unnecessary hysteria to me.