Straight from the rpi-open-firmware repo:
> Does it boot Linux? Yes, with some conditions. You can boot a very minimal version of Linux without the firmware and get it to work with UART and eMMC. Support for USB, DMA, and Ethernet are in the works.
The default firmware and Raspbian environment involve many non-free blobs.
In the case of the open-source VC4 drivers (GPU driver), these are being written by a Broadcom employee (in his spare time). Broadcom are the company behind the SoC that is at the core of the RPi. So you have a person with access to technical documentation from the company that makes the device writing the drivers. Regardless of whether they get paid or not, the drivers are of high quality, they've even made it into mainline Linux, so they work out of the box. There's very few SBC that have similar levels of open source support for their GPUs.
As for the firmware, yes it does need more work to be a true replacement for the standard one. However, it's a fixed target, and there are people willing to put in the work, so it's only a matter of time before it improves further. That said, I'm sure more assistance would be welcome.
Unfortunately, the current end result seems to be a Linux that doesn't even have support for USB or ethernet.
There are so many SBCs these days it's hard to enumerate all of them, but this board looks more open than RPi. I think it uses Vivante/Etnaviv graphics. http://www.imx6rex.com/open-rex/
That's over 5x the price for the cheapest model (iMX6 OpenRex SBC Basic, €199 in quantity 1, http://www.voipac.com/#category3 ), at that price you'd be better off getting an x86 board.
> "Unfortunately, the current end result seems to be a Linux that doesn't even have support for USB or ethernet."
You forgot a word at the end of that statement... " yet". Furthermore, expensive outliers like the OpenRex aside, it's still currently more open than its main competition.
That said, I shouldn't be so critical. The state of free graphics drivers on ARM SBCs is pretty abysmal and any improvement is a good thing. Mostly I object to the assertion "RPi is a free and open platform," but rereading your original post you didn't actually say that. Perhaps we should say "RPi is one of the least-closed platforms." It will be great to see the FOSS VC4 drivers mainlined into the Linux kernel.
Survey of FOSS ARM graphics drivers https://www.phoronix.com/scan.php?page=news_item&px=MTQ3MTM
Hardware that can run the Lima free graphics driver: https://limadriver.org/Hardware/
Hardware that can use the Etnaviv free graphics driver: https://github.com/etnaviv/etna_viv#socs-with-vivante-gpu
I said "most open". You said "least closed". In my opinion that's the same thing, just with a different spin.