Changing Character Government type? Crusader Kings 2

With the Horse Lords expansion, it is a lot harder to switch your government type. I'm playing as a tribal Irish character, in the north of Ireland.

I can't find anyway to switch from Tribal to Feudalism, and I can't find the answer online, anywhere.

How do I change government type in Crusader Kings 2: Horse Lords?

In order to become feudal you need

• The Cultural Technology called Noble Customs 1
• Your capital needs to be a fully upgraded Hillfort, which requires the Economy Technology Castle Infrastructure 1
• If you are independent you need to have the Absolute Tribal Organization Law. This requires the Cultural Technology Legalism 1 If you are not independent you need your Tribal Liege to have Absolute Tribal Organization, or you need to have a Feudal Liege.
• If you are independent you must not be an Unreformed Pagan. (most likely not relevant for your Irish Chief who is probably Catholic, useful to know in general)

Once you fulfill all of these requirements it will unlock the Decision to Become Feudal. When you take that decision all your Tribal Holdings will convert to Castles (possibly with some buildings if you have upgraded the Tribal Holding according to the charts on this page) and it will automatically build Cities and Temples in Counties that do not already have one. It will not fill the final holding slot.

The CK2 wiki answers that quite well.

You need to :

• research the technology Noble Customs 1

• build a Stone Hillfort (last upgrade of the Hillfort), requiring research of Castle Infrastructure 1

Then you will be able to adopt feudalism.