We see others have provided a lot of good ideas here.
Our perspective.
The key thing is whatever you choose it must be something you would want to do for a long time and never tire of helping people with it.
Ideally it would be with something you have a lot of knowledge about so you don't have to spend as much time researching. If writing is challenging for you having experience in your niche makes learning the skills of writing so much easier. Too many new things at once is overwhelming.

You can get a perspective on niche volume interest and if it is seasonal or evergreen using the trends dot google dot com.

Also you may want to look for the common questions people have in your niche using usetopic dot com/. people-also-ask to see if that inspires.

More important than finding a profitable niche is finding one you know and love enough to be able to write quality consistent content about.
You will always find ways to monetize a site, getting good content out regularly will rank your site in Google, and that will make you attractive to affiliate programs and then you can earn from the site.
Trying to pick something that sells profitably is not the way affiliate marketing works, your product is your content, the profitability comes from traffic and your potential to promote.
Pick a niche you are familiar with and you can talk about for hours, then turn talk in to posts and you're away

Hi Gary!

I just going through your profile story and I saw you are a paint decorator.
If that is something you love to do and you passion about it, you can write articles about it. you can teacher other how to pain, pick the right paint for the right surface, indoor , out door, ,,,
Answer this question , I want to help people with ,,,,,,.
fill in the blank and you will have your niche. come up with couple more and pick out the one you like the most.

Hope this help,

Jason

Hello Gary,

It is quite understandable.

What is it you want to do that you have
more knowledge about and more
experiences about?

What are you fond of doing as a hobby
or a work that you love doing on a daily
basis that you can give the important
information to others that will help them.

When you were a child, what is that one
or two things that you always wanted to
do and excited about that you can help
other people and eventually give them
the necessary need for their lives.

Bear in mind that you will be writing a
lot of content based on your niche
and you have to write valuable content
that will benefit your readers or potential
customers eventually.

Have a read about this, link, please? Choosing Your Direction - It Starts With a Niche Hope this helps.

Blessings.

Elizabeth

H, Gary.

As Dale has asked, what are you passionate about?
What do you enjoy?
What are your hobbies and interests?
What can you talk about for hours?

These are great questions to start with.

Here are some other pieces of content that may also help you: Coming Up With Niche Ideas / Idea Generation Researching and Finding an Evergreen Niche Top 6 Evergreen Niches Offering huge Profits in 2021 I trust that these will help you.

Cassi