How to add "text entry" to the question and not an answer choice?

This is not possible via the default functionality. You'll need some level of HTML/JS programming to get it done.
However, since you already have these questions in the survey, just copy them and change the text.

https://www.qualtrics.com/community/discussion/comment/36152#Comment_36152"However, since you already have these questions in the survey, just copy them and change the text."
I didn't understand this part

You mentioned that you already have questions like these:

How do I do the HTML/JS thing to get it done? I'm not an expert in JS or HTML

OMG! Thank you so very much! That's exactly what I needed. I'll ask you more if I come across other problems. Thanks again man!

https://www.qualtrics.com/community/discussion/comment/36218#Comment_36218Thank you for this JS code.
Today I wanted to analyse the responses but I do not see a single "Comment" in the comment section. Is it possible it did not work in saving their comments?

You'll need to create an embedded variable for each question. See the survey flow to see the format.

https://www.qualtrics.com/community/discussion/comment/36586#Comment_36586Sorry, I do not understand what you are talking about.

Since the comments field is being added via JS, if you want to see what's entered in them, you'll need to create an embedded variable for every question where you are doing so.
In the attached QSF, see the survey flow. Before the comments question is asked, an embedded variable is defined in the format of QIDxx_Comments. So, if you've got 40 questions like this, you'll need to define 40 embedded variables, with the same format.
So it may be like QID7_comments, QID45_comments, QID132_comments etc.
The QID varies for each question. Read up the support pages to find it.
In the attached QSF, because the id of the question is QID1, you see that the embedded variable is QID1_comments.