Who was ignorant about the Truth in the beginning?

In the dependent origin co-arising, ignorance came before consciousness and self.

Very good. You are starting to learn. Soon, "you" might be a Buddha & become our teacher!

Who is ignorant about the 4 noble Truths in the beginning of dependent origin co-arising.

The mind (citta) is ignorant (rather than a "who" or "self'). Please read SN 12.12, which answers the question of "who". AN 10.61 (about ignorance as the 1st cause) is also helpful here but complex.

ignorant... when there was no self or consciousness?

Ignorance does not cause consciousness. In your studies of Buddhism, please avoid this materialistic error that most Buddhists have. As a beginning student, it is important to learn the right way, from the beginning. The suttas (SN 22.82) say consciousness is caused (hetu) by the mind-body (nama-rupa).

In reality, dependent origination is describing how ignorance pollutes consciousness, similar to how dirt pollutes pure water or how dust covers a mirror. SN 46.55 provides some good analogies.

This is why there are many suttas that describe how a Buddha has no ignorance but remains conscious, such as SN 22.53, Iti 44 and the end of MN 38.

How can ignorance exist without consciousness ?

This misunderstanding I have already answered above. However, this being said, ignorance can exist without consciousness however only as an 'underlying tendency' ('anusaya'). For example, when the mind is in deep sleep at night, it is not conscious. But whatever ignorance remains in the mind still remains dormant; similar to how memories remain dormant in the mind while the mind is sleeping unconscious.

Component in each dependent origination is not parent and child relationship. One is not giving birth to the next. They all are circular dependency or depended on each other to exist. Like planks leaning on each other, they both support each other and without one, it would fall. And "who" is best to replace with "what" as seen as many suttas. The Sheaves of Reeds

I have evolved a little since asking this question. I will try to answer the question.

First and foremost let us understand that not everything that has been written can be understood fully with proof as we generally stop at the theory. We never fully live the path as preached by Buddha. Only a Buddha can understand some part of the theory because he has experienced it directly. Having said that it is clear that the question can be answered.

Who was ignorant about the Truth in the beginning? Answer is that we can not ask this question. This question is wrong. The question assumes existence of Self before the origination of Ignorance. The fact is ignorance led to the emergence of Self. The right question should be : Ignorance is a condition for what ? Answer would be Ignorance is a condition to origination of merit and demerit. Merit and Demerit are condition to what ? Merit and Demerit are condition to Consciousness. Consciousness is a condition to what ? Consciousness is a condition to body and mind ... and so on...

I must admit we do not know answers to some questions like :

1. How did Ignorance first arise?
2. To what ignorance was then attached?

I guess one needs to practice the Truth in order to experience the answers directly. If you have the answers please share.

"Who is ignorant about the 4 noble Truths in the beginning of dependent origin co-arising when there was no self or consciousness?"

You were ignorant.

Being ignorant, you created self.

Being ignorant, you created consciousness.

"How can ignorance exist without consciousness ?"

It cannot.

Where there is ignorance, there is consciousness.

Where there is wisdom, there is no consciousness.

It's because you don't know what is consciousness, that you are bewildered by my answer.

And what is consciousness?

It's a fabrication. It's made up. It's fabricated with mental and physical activities. That is consciousness.

It is you fabricating this consciousness.

Now ask yourself, who is that "you" that I'm referring to in my answer?

No matter where you'd look, you would not find this "you".

So, who is ignorant if there is no "you" that can be found?

You is ignorant.

It's because you don't know who you are, that you are bewildered by my answer.

Find out who you are. Meditate. You will not find this "you". It's when not being able to find this "you", that you are seeing who you are. Once you see, examine how it works and truth will be realized: from ignorance arises fabrications, from fabrications consciousness, from consciousness birth, etc.

There is no permanent eternal self. But there is still an impermanent self, that arises out of the inter-working of the five aggregates, that arises and disappears. This self is the doer. This doer-self (or rather the citta - mind-stream?) was ignorant.

Remember the middle way between eternalism and annihilationism.

The commentary on Attakārī Sutta by K. Nizamis:

“Natthi attakāro, natthi parakāro.” (‘There is no self-doer, there is no other-doer.’) Some people might have expected the Buddha to have approved highly of this naïve negative doctrine. The fact that he very succinctly and effectively refutes it is extremely instructive and of great significance for gaining a better understanding of the depth, subtlety, and holism of the Buddha’s actual teaching. Although the Buddha taught that there is no permanent, eternal, immutable, independently-existing core “self” (attā), he also taught that there is “action” or “doing”, and that it is therefore meaningful to speak of one who intends, initiates, sustains and completes actions and deeds, and who is therefore an ethically responsible and culpable being. It should be quite clear from its usage in this sutta, and from the argument of this sutta, that kāra in atta-kāra must be an agent noun, “doer, maker”: this is strongly entailed, for example, by the Buddha’s statement: “ārabbhavanto sattā paññāyanti, ayaṃ sattānaṃ attakāro ayaṃ parakāro”, “initiating beings are clearly discerned: of (such) beings, this is the self-doer, this, the other-doer”