So currently the project is nothing but a proof of concept with a solid base component (pmbootstrap).
I guess with "production phone" you mean, that it can compete with Android/Apple? This would take years, and that isn't in the scope at all for now.
What is a goal though is to make basic functionality work, so you could at least use Wi-Fi, do phone calls, update your phone and have a sane userland (where programs don't run as root, when they don't need to and ideally have privilege separation). Even for that it's hard to estimate, but maybe half a year or so.
So I'm optimistic :)
On this point, have you considered using Snaps or Flatpak? Before Canonical pulled the plug on Ubuntu Mobile I believe they intended to use Snaps for most/all userland software. Though I'm not a Linux expert, it still seems like a solid idea.
He is using the Alpine Linux user space for that.