Can the unchained monk use any archetypes??

[noble peasant]

I didn't think they could but someone mentioned to me that they could've swore there was one that could be used.

[Chess Pwn]

there are now 2 archetypes that are designed to work with UMonk.
Monk of the Mantis and Serpent-Fire Adept

[Zhayne]

If you do 3pp stuff, check DriveThruRPG. I know I saw that someone had rejiggered all the extant Monk archetypes to work with the Unchained Monk.

[Shiroi]

Yeah, technically there's a couple new archetypes designed for unchained and that's it. But I've made the old monk of the four Winds work on the new monk just fine, it's not hard.

It seems for the most part that you can't use old archetypes because they replace class features which became ki powers.

If you lose the ki power selection at the appropriate level, and ban the ki power itself altogether at any level, then you've lost the same options and the same number of options. For most archetypes this will be plenty sufficient for a comparable trade. A few might require DM discretion to prevent awkward interactions, particularly around archetypes which are very clearly based on being a 3/4 bab class or which modify flurry of blows. Remember Unmonk is more mobile as well, so anything archetype wise that alters mobility might need to be rebalanced to account for the changes.

[JonathonWilder]

What you need is Everyman Unchained: Monk  Archetypes I & II found here and here. These books fully convert each of the Monk archetypes available for use with the Unchained Monk, and the way they do so make sense/work out well. Just make sure it is okay to use them since the books are 3rd party.

Still, if the DM is reasonable and willing to look through the books themselves I do believe they would be willing. Especially since the Unchained Monk is otherwise all around less attractive of an option for players, with no archetypes really available to them.

[Derklord]

While the book doesn't say that, there are a few archetypes that only replace/alter monk class features that unchained left at that level: Harrow Warden, Master of Many Styles, Sensei, and Weapon Adept. Note that Master of many Styles's Fuse Style ability follows the old FoB progression (1/8/15), but that shouldn't be a problem.

Hamatulatsu Master should work just fine, too (you get the changes to ki pool one level earlier, but that's not exactly game changing).

The Monk of the Four Winds archetypes works if you simply rule that you replace your 12th level ki power instead of Abundant Step.

There are a lot of archetypes can be adepted with the blueprint given by Monk of the Mantis from Dirty Tactics Toolbox and Serpent-Fire Adept from Occult Origins, but you would have to work with your GM if you get the abilities one level earlier (like Monk of the Mantis does) or later (like Serpent-Fire Adept does).

@JonathonWilder: UnMonk isn't as much in need of archetypes as core monk is (and an improved version of Qinggong is already included). A few archetype abilities have even been made into ki powers (like the Drunken Master's Firewater Breath).