Check LibreCMC (which is a free - as in freedom - GNU/Linux distribution)
From LibreCMC web page:
https://librecmc.org/librecmc/home
[…] entire list of supported hardware for libreCMC v1.3.4
https://librecmc.org/librecmc/downloads/snapshots/v1.3.4/ar71xx/luci/
LibreCMC - Wikipedia
https://en.wikipedia.org/wiki/LibreCMC
LibreCMC is listed in lists the GNU/Linux distributions:
http://www.gnu.org/distros/free-distros.html
*I think which if you want to use QoS you will probably need to install
additional packages (you can do it from web user interface if you don’t
want to use console -Telnet or SSH-).
**OpenWRT isn’t free because contains blobs.
