It doesn't seem like it would be an option for those incapable of work. And, it's unlikely that there's enough actually beneficial state work going around for everyone.

It's not really economically sensible for the state to make up busywork for people in CCC because there isn't enough real work. The cost of arranging such work would, I'm sure, outweigh the meagre benefits it would bring. You might as well pay the workers directly and not have them do the busywork, but that's essentially the same thing as basic income.

If the scheme didn't support everyone regardless of their ability to do work and the state's ability to provide work, then CCC would be "just another" benefits program, rather than something which could, in principle, replace virtually all current benefits programs.

Having said that, I'm not opposed to the idea that people who are long-term unemployed in a basic income system could be required to work for the state in some capacity, when legitimate work is available.

You provided the lord with a certain amount of labor (which varied considerably at different times and places), and the lord gave you a hovel and enough of the food you grew to survive.

I don't think we want to go back to that, really.

UBI, in my understanding of the term, is something else. If it requires service in exchange, it's not UBI.