Praise be to Allah.
There is nothing wrong with those who build and sell houses installing cables for TV, unless it is known or thought most likely that a specific purchaser will use the television for haraam purposes. If it is not known what he will do, then there is no blame on the builder.
This principle is stated by the fuqaha’ with regard to the ruling on selling anything that may be used for sinful purposes, such as selling grapes to someone who will press them to make wine, or selling weapons at times of fitnah and civil war.
Ibn Qudaamah said: To sum up: selling juice to one who it is believed will use it to make wine is haraam, and ash-Shaafa ‘i regarded it as makrooh. Some of our companions stated that if the seller believes that he will use it to make wine, then it is haraam; he only described it as makrooh if there is uncertainty concerning that…
Once this is established, the sale is only haraam and invalid if the seller knows that the purchaser intends to do that, either because he said so, or because of circumstantial evidence which indicates that.
But if it is only a matter of possibility, such as if it is bought by someone who is not known, or by someone who makes both vinegar and wine, and he did not say anything to indicate that he wanted to make wine, then the sale is permissible.
The same ruling applies to everything which may be intended for haraam purposes, such as selling weapons to fighters or bandits, or at the time of fitnah or civil war, or selling female slaves for the purpose of singing or hiring them out for that purpose, or renting his house for wine to be sold in it, or to be used as a church or fire temple, and so on. That is haraam and the transaction is invalid, for the reasons noted above. End quote from al-Mughni (4/154).
It says in al-Mawsoo‘ah al-Fiqhiyyah: The majority are of the view that with regard to anything that may be intended for haraam purposes, and any transaction that will lead to sin, it is haraam.
So it is not allowed to sell anything of which it is known that the purchaser intends to use it for some purpose that is not permissible.
End quote from al-Mawsoo‘ah al-Fiqhiyyah al-Kuwaitiyyah (9/213).
So if it is known that a specific purchaser intends to use it for haraam purposes, based on something that he said or based on circumstantial evidence, it is haraam to install it for him.
But if nothing is known about the purchaser or his situation, as is the case in your question, then there is nothing wrong with that.
And Allah knows best.