kmielke What about a partnership with a company that makes sustainable smartphones?
If a company makes sustainable smartphones and has strong hardware security and quick firmware and Android updates, that seems like a possible partner.
kmielke The German company SHIFT [...]
Their web site says the SHIFTphone 8 is running Android 14? If true, that sounds like a hard fail in terms of timely security fixes.
The GrapheneOS device requirements are here: https://grapheneos.org/faq#future-devices
I am pretty confident that the project leaders are not opposed to sustainability, but I suspect they are unwilling to give up on strong security to get sustainability -- especially now that Google's support lifetime is fairly reasonable.