I will do my very best to reply your question. Keep in mind, as specified above, my SEO is rusty, and I'm actually upgrading my skills this coming month.
No, there should not be a canonical tag at all on the index page. I think the paragraph that I posted from my new SEO agency makes it apparent. Whether you believe in juice or not, the primary focus should be your index page, which should be your main root URL.
Telling Google that you are deflecting your main root URL to somewhere else, or transferring your juice to another page, is not a good idea, especially when it's the root of your website, your main door.
I understand that Ablecommerce, because of its module design, has given this page a default name of "default", but the problem is, it still loads as "default" and now competes with your main root URL. To make it even worse, you are now telling Google, that this should be your main page and not your root URL. In other words, you're transferring your juice somewhere else. Of course Google can disregard this, but why would you do this in the first place?
You also might have noticed that I have done a redirect back to the homepage in the event you were to try to go to the default page.
Duplicate pages sometimes exist because of the way shopping carts are designed. For instance, another duplicate page exists for my homepage at "https://www1.myradiomall.com/", but I'm not telling Google to go there.
We have moved to AbleCommerce from a shopping cart that we have been using for 20 years, we are constantly on the Google Search Console fixing errors, some of them which are actually created by the way AbleCommerce functions. We are on top of this, and so far, we have been able to rectify many things.
I know that you have an SEO team on your staff, unfortunately I was not happy with them and had to go someplace else for this very reason. The foundation of a website needs to be fixed first before trying to implement any type of keywords enhancements. Everything begins with your homepage, not a good idea to ask Google to go someplace else.
Just my thoughts, we can discuss more on the phone if you wish.
Thanks