The plan, especially when it comes to modems and graphics acceleration, is to package these firmware blobs separately. Then, a user can choose at install time if they're alright with non-free blobs running on their phone. This has already been done for many phones for WiFi/Bluetooth chipsets.
This method also has the advantage of letting us move quicker - we don't need to wait years to reverse engineer modem firmware, or be required to spend the time mainlining every device we want to add in order to get the "essential" features for a phone.
(I'm a developer on the project)
Me personally I'm fine with framebuffer drivers, I don't need hardware acceleration. So that needs no blobs. For some Qualcomm chipsets you can get 3D acceleration working without blobs using freedreno.
I personally started working on getting the qualcomm modem userspace blobs working under pmOS[0].
If you just want pretty much everything to get to work, there's also the halium project[1] which runs a stripped down android in an LXC container to provide that stuff. This could easily be ported to pmOS too.
It really depends on how libre you want your phone to be. Android applications could probably be run on pmOS too using e.g. Anbox[2].
One example: https://wiki.postmarketos.org/wiki/Samsung_Galaxy_SII_(samsu...
(I'm a developer)
Would love there to be something that provided just enough glue code between HAL and, say, Qt, alongside a bunch of shell scripts for gutting images of common handsets. But getting there myself, I've really little clue about this stuff, but I'm sure there is tribal knowledge buried all over the forums the Android dev community use