https://wiki.postmarketos.org/wiki/Nokia_N9
It cannot be flashed currently, only starts by preloading kernel and initrd over USB to RAM.

But as we already got multiboot for n9, it should be pretty easy to start from it from internal flash memory.

But as with SailfishOS/FirefoxOS/Android you will have crippled OS support(because of old kernel) or lack of bluetooth/telephony/bme[battery charging], etc (on new kernel).

So this OS will be as usable as other 3rd party OSes ported to n9, unless somebody will backport old drivers to new kernel (so we are again back to the point kernel-update-project for n9, which never succeed and there were 2 big attemps).

I really wish the best for this project and love n9(it's still my daily driver), but after looking past, I'm a bit sceptical...

@danpio: Aren't you BeOS fan that uploaded some image for me maaany years ago?

BTW, I would love to have white n9 :-/