It's a big question. I know.

But given that we have the source code to Android (AOSP) and the community to collaborate with, couldn't we just create an entire ROM filled with the necessary applications and utilities, all open source, and with modern UI?

It'll take a shit load of time, and effort. Definitely. But maybe if we banded together? A unified OS running only open source software, with the option for Google Services via something like MicroG, so that we don't need to worry.

I'm no expert. I'm just floating an idea. But I'd love to know if this is possible, step-by-step...

Edit: I know custom ROMs are a thing. I use one. I'm just saying, what if we go ahead and make an open source ecosystem that runs under the same project, so that there's a set of services and apps that are free, open source and non-corporate.

Edit2: I forgot the Lineage project exists. Nevermind 🤦🏻‍♂️. Let's just try to support it. 🙌🏼🙌🏼🙌🏼