How do I count "Distinct" text items using a "Subtotal" function to exclude count of filtered or hidden line items.

Question: How do I count "Distinct" text items using a "Subtotal" function to exclude count of filtered or hidden line items.

I wanted to count the "Distinct" Product Groups in the list of 21 items (product groups counted once for repeating line items).

I came up with 10 "Distinct" Product Groups using the following formula:

{=SUM(IF(ISTEXT(C11:C31),1/COUNTIF(C11:C31, C11:C31),""))}

(The formula requires the CTRL + SHIFT + ENTER keys to be selected when done editing the formula for it to work and to add the "{" and "}" curly brackets at the start and end)

This is great to count the product groups used in the list when a much larger list is used or a report of specific groups that are exported. However, I am having trouble converting it to a "Subtotal" version that would only show "Visible" items that are "Not" filtered or hidden. Any ideas? Would this be a substitution for the SUM and COUNTIF functions with Subtotal versions? I am using Excel version 2019 2308 Build an tying to do it in one formula without helper cells, if possible. Thanks!