just bought me a Scarlett 2i2 (2nd gen) & Rode NT2-A today to do some guitar & vocal recording.
I might be able to test some stuff for you the next days on Ubuntu 16.04 LTS - that is if you bear with a recording newbie along the way

So far I could get the 2i2 to record in Audacity (didn't get Ardour 5.9 to work yet) - pretty much plug 'n' play experience.
What was unexpected is, that turning the gain knob didn't seem to have any effect on the recording levels - for me those were always at around -50dB to -40dB and I constantly need to add approx. 20dB in Audacity to get to well audible levels. Noise levels were no issue (if any, probably driven by my cheap headphones) & clipping seemed far away - I guess rather a nuisance in post-processing than anything else, but maybe I'm missing something important here?!
The headphone jack output worked after I had set the output in Audacity to 'Scarlett' (USB device was detected to my surprise) - the playback volume could be set to all reasonable levels for my taste (especially after the above mentioned 20dB adjustment in post-processing).
The direct monitor function worked - though there was a rather small adjustment sweet spot to get in work. I basically had to max out the microphone gain level and nearly so the headphone volume (to

Again, I don't know whether this is supposed to work that way in that price range, was due to my inexperience, the OS or my cheap (inappropriate impedance level?) phone headphones (--> any valuable tips or my headphone upgrade for the given combo highly welcome).
@ Admins: pls. shift this article to where appropriate, in case it doesn't fit ...