Mandalorians are pretty much everywhere in the galaxy. Almost every faction on Chaos has a handful of Mandalorians running about in their ranks. I know a fair number of them (at one point) were wandering around the Outer Rim Coalition, and a handful have found their way into The Sith Empire and the Confederacy of Independent Systems. The core faction of the moment used to be called "The Mandalorian Empire" and was very "nobility" themed with strong political ties with The Sith Empire. The faction recently re-branded itself as The United Clans of Mandalore, or something along those lines, and it's going through a bit of a transition phase. Pretty much everyone is at war with the Mandalorian faction at the moment, with most of those factions seeing the Mandalorian faction as a weak puppet kingdom that serves at the beck and call of the Sith.
Think North Korea and China.
Recently, TSE announced an invasion of the planet Mandalore in an attempt to establish stronger control over areas of space that the Mandalorians seem to no longer be strong enough to protect on their own. Several of the distant Mandalorian characters that wanted nothing to do with "The Mandalorian Empire" are planning to return to protect their homeworld from the Sith.
The Mandalorian Empire has a shady past. At one point they rounded up people, kids included, and shoved them in prisons and forced them to take drugs that would sever them from their connection to the Force. There were a few crusades, some disturbingly close relations with one Sith Lord or another, some creepy, black eyed children were born, and other decidedly "un-Mandalorian" things. At least, "un-Mandalorian" in the eyes of those who had written for the previous Mandalorian factions of the board.