Sailfish OS - they even run a device preorder right now.

But is it open? Seems not; parts are closed so is that not just more of the same?

postmarketOS, Mobian, PureOS are open.

Yeah, some bits (parts of the GUI & some of the default apps) are still closed.

But I think there is a good chance they will finally open those now - never really made any sense to keep them closed and preventing the community from contributing. Rumors had it it was due to non-cooperative investors.

Not Jolla is finally independent again, so at least in theory they can finally do the right thing. :)

GrapheneOS is Android's last hope. They're making great progress with deals with smartphone manufacturers. However, the threat of remote attestation looms eternal. I have essential apps that I cannot afford to lose and if they refuse to work on a non-Google phone the usefulness of GrapheneOS is severely degraded.

If attestation ever became ubiquitous the difference between iOS and Android would cease to exist for me. I'd need a black box that lived in a desk drawer for interfacing with specific services and otherwise I'd cart around a camera in my pocket that happened to double as a linux tablet.

No, the solution is having a linux micro-computer. You buy an iPhone shitphone to do banking and whatnot, and never touch it, then just do everything you need off a retroconsole since it runs literally 120% of the other apps a phone would.