What do you want out of a Linux phone?
Some things I want that android/chroot doesn't offer:
A good terminal interface
To be able to script things that, to my knowledge, a chroot doesn't let you: texting, change alarms, sounds, etc.
A real browser, not a mobile browser
A phone that is actually free (as in speech)
And these are just off the top of my head in the past 5 minutes. If I actually sat and thought about it, I'm sure I could come up with many more.
http://bonedaddy.net/pabs3/log/2012/12/03/debian-mobile/
I wonder if any of these terminals work for you:
https://f-droid.org/repository/browse/?fdfilter=terminal&fdi... https://f-droid.org/repository/browse/?fdfilter=terminal&fdi...
A chroot will indeed not be able to change Android things.
I would guess "real browser"s are either too slow or memory bloated to work on mobile devices and either way their UI isn't going to be usable on a small touchscreen device probably..
When you talk about free as in speech, there are so many layers there it is hard to know which parts you are talking about, here are some:
Do you want the minerals used to not be involved with wars, slavery, suicide in factories and other nastiness? Fairphone is working on that but freedom on the software side is not really one of their goals.
Do you want the phone to be repairable rather than discarded every 2 years? Fairphone is working on that too and just came out with a modular device.
Do you want to run a patent-free CPU architecture with FLOSS-licensed CPU designs? RISC-V exists bit is in the early stages. lowRISC aims to produce ASICs but hasn't done so yet.
Do you want the phone case to be manufactured using the LulzBot libre 3D printer from FLOSS CAD designs produced in freecad or similar? The OpenMoko FreeRunner had libre designs but they weren't produced with libre tools IIRC and they were pretty chunky physically. The Neo900 case is just from discarded N900 devices, but the motherboard and baseband isolation features are excellent.
Do you want the baseband to be running FLOSS-licensed software? OsmocomBB only supports 2G and parts of it have to run outside the baseband.
Do you want the other chips (WiFi etc) to run FLOSS software? There are some (ath9k_htc, OpenFWWF, carl9170.fw, prism54 FreeMAC) but none of the WiFi chips typically used in phones and most are dead projects.
Do you want a FLOSS operating system that supports arbitrary mobile hardware? Mainline Linux doesn't support many mobile devices and the mobile device industry moves so fast that there isn't really time for them to upstream their code before shipping the device.
I recommend looking up bunnie huang's ideas about layers of freedom and the hardware world.