There isn't a switch that flips and everything suddenly becomes completely 100% decentralized and all centralized production ends.

:D HaHa! That made me laugh, since I guess that you know that I know that.

It is entirely possible to mine, smelt, and produce iron alone.

What do you mean by ‘alone’?
To make steel, you have to take the raw material, such as iron ore, out of the ground.
"0.1 tonnes of crude steel requires around 0.14 tonnes of saved iron ore."

Do you walk into an iron ore mine or quarry and dig it out of the rock by hand?
If you have no access to a mine, you know where to dig? What if this land is not your property?

So even if you are able to melt steel using modern electric furnace technology, you still have to refine it afterwards or use other raw or refined materials to make a finished conductor board.
Everything stands and falls with the initial mining of raw materials. If you don't have access to these, you don't have decentralisation.

"The conductor tracks required for the PCBs themselves are usually etched from a thin layer of copper (typically 35 µm) and applied to the insulating substrate. However, there are also other materials, such as aluminium or stainless steel, which can be used as conductor material." --> AI research.

Recycling instead of mining:
Even if you extract the materials for the circuit boards from electronic waste, you first have to collect it in relevant quantities, store it somewhere and then extract the copper (and gold, silver etc.) from it using mechanical, chemical and electrolytic processes.
From where do you get the electronic waste if you want to catch it before it reaches the usual places?
You need a truck to load the material
you need storage room
you need a production room
you need more than one hand
you need the intelligence during the manual process of using chemicals (most importantly: where do get chemicals?)
you need a lot of energy
you need customers
distribution/trade
etc.

Having said all this, I would be delighted if decentralization happens more, and more small businesses take place. I am all for it. But you'd have to convince young people to educate themselves in all these matters like agriculture, transportation, communications and construction. The majority of modern youth and later adults are consumers, not inventors. To make such significant shift, you'd need universities who teach you decentralized concepts and methods and push that mindset. Who shall teach, if that is not happening? The internet? Well, it has its limits.

Let's say there is one local business who produces PCBs. We agree, that alone isn't enough, you'd need all other local businesses you mentioned. That requires already a city of people and private property and a certain radius in order to collect or purchase the materials required for all these economic sectors. There is the devil in all these details.

In order to build something like a self sustainable town you'd need coordination between these businesses and you'd need to coordinate with neighboring local towns and businesses, since there will always be a lack of needed materials and some scarcity.

I like the very idea of decentralization very much. Don't get me wrong. I just don't see anyone near me and I know no one in person who does such things. Do you?

So, I am not an expert and since I do not live and work in an eco-village and since you do not either, I think we are just some consumers (me more than you) who like to think of a future for our children which is less dreadful.