I just posted this reply in response to my original post, but in case this is still helpful, this is all the info that I have so far.

T2125B = business income

T2125P = professional income

T2125C = commission income

T2042 = farming income

T2121 = fishing income

The numbers 1-4 in each category correspond to the numbered business or professional activity you have listed. So if you are self-employed and only have one business, choose T2125B #1. If you have multiple, T2125B #1 for income related to Business 1 and T2125B #2 for income related to Business 2 and so on.

Re the numbering, I've been told that the numbers 1-4 in each category correspond to the numbered business or professional activity you have listed. So if you are self-employed and only have one business, choose T2125B #1. If you have multiple, T2125B #1 for income related to Business 1 and T2125B #2 for income related to Business 2 and so on.

The only thing I got from calling turbotax helpline  was a suggestion to buy "assist and review"  

@aj knight To check what industry code applies to you, please refer to this CRA guide: North American Industry Classification System (NAICS) Canada 2022 Version 1.0

That's honestly the type of conversation that I was expecting... low expectations going in only leaves room for me to be pleasantly surprised when I instead encounter a helpful attitude and accurate advice.