GrapheneOS has been working flawlessly for me for years. Highly recommend!

I'm an /e/os user and all I can say is even though it sucks the least among its competition, it STILL SUCKS! Not to downplay the immense effort put in by the devs and maintainers of course. Providing a privacy-respecting phone OS to ordinary people isn't just a good deed, it's necessary for a vibrant and diverse digital society. But still, we can all strive for better.

Just one problem. Both are still dependent on Google and Android-based. How sustainable is that security model when a company has the say-so over whether you get to flash your custom firmware next year, or the next year, or maybe the year after that?

Check out crDroid. I do not know how it's like to daily drive it, but afaik it's highly customizable.

Yep, they put in a lot of effort into the security and open source stuff, but at least on Graphene, the bundled apps are severely outdated aosp apps, they don't even support material you, meanwhile current aosp apps do support it, as can be seen on Lineage. The calculator app looks straight from Android 5 or probably earlier.