Firmware and booting questions, Librem 5 phone

Hardware Librem 5
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Has any information been released about the options for tinkering with the firmware and/or booting different OSes on the upcoming Librem 5?

The most basic question: having a choice of OSes is an important feature of this phone, so what is the expected procedure for installing an OS?

On a PC platform, you would use a bootable flash drive or optical disc to load the installer, which makes it quite easy. On ARM platforms, bootable media does not seem to be standardised. Will the firmware on the Librem 5 enable a similarly easy procedure?

What methods will there be for flashing new firmware?

Will the firmware have any configurable parameters, like a BIOS, or will it be more of a keep-it-simple-stupid approach where the firmware is little more than a bootloader and the OS deals with any adjustable parameters?

On embedded platforms, a serial port can be useful for tinkering with the bootloader, but I suppose on a device with a screen that’s less important (assuming the bootloader is capable of driving the screen and a USB keyboard).

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Relevant Purism news post describing some details of the i.MX 8 boot process.

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bump.
Article is nice but a bit old and some links don’t work any more (http://processors.wiki.ti.com/index.php/The_Boot_Process).
It would be really nice to know how to Librem 5 boot process works, from the reset vector till user-space loads. (when U-boot comes into the picture, etc)

  1. What is code that exists in the chip’s ROM? Is that open source? Was that coded by Purism and the manufacturer added to the chip?
  2. What is the SPL (second stage boot loader)? Again is that open source?

Good video to watch on the subject: https://youtu.be/GXFw8SV-51g

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Here is the same video proxied through my Poke instance:

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