waa get 5.1 chael configuration with MB Asus H97M-E + Xubuntu

Hi!

My motherboard is an Asus H97M-E. Only three basics, typically "2.1" ports at the back of it (blue/line in, pink/mic, green/line out), so I thought it meant I had to add a sound card on PCIe to handle the [black-rear, orange-bass, green-front] jack coecters of my 5.1 speaker kit I recently bought.

Yet here's what my MB configuration says:

It happens that apparently my MB should handle 5.1, even 7.1, natively! Apparently the three ports on the back should, depending on the "chael configuration" (2.1, 5.1, 7.1) behave differently, and if I'd be in an 5.1 config, the blue entry should work as a black one, and the pink as an orange one. If I wanted to get hypothetically a 7.1 config to work (which I don't though ^^), apparently I'd have to set, in the BIOS I think, the front panel port entry, as the "fourth port" aka as the port for the surround speakers (chael 7 and 8, considering the 5.1 has 6 of them technically, again *apparently*, coz if it's not clear at this point I'm a dabbler more than any kind of cooisseur, in sound technology)).

Hence, I'm trying desperately to find how to make my MB/OS realize that I'm in a 5.1 config, and thus that I want the blue/line-in to behave as a rear/surround 5.1 jack entry, and same for the pink/mic, as an orange/bass-center, if you follow my wording.

So far zippo: nothing in the BIOS, nor in PulseAudio control panel. I even tried to find the Windows Software used by the Microsoft users, called Realtek HD audio manager, and supposed to help decide what kind of jack you put in your motherboard. Again, weirdly, I only find drivers, but would it be that? didn't try, plus unless I'm strongly mistaken, windows drivers will do no good on linux, except maybe inside a Virtual Box...

Anyway, I just want to use the 5.1 chael configuration supposed to be supported by my MB, albeit in a way that seems weird to me! (double behavior of sound ports).

Anyone got it all? Knows how to help me? Please do so, after a whole 12h around GoogleLand without so much as a tiny half-result, I just got outright desperate ^^
Thanks a bunch in advance, have a nice day!