I tried several combinations, none of which worked:
if (is_home()) :
if (is_front_page()) :
if (is_front_page() && is_home()) :
if (is_front_page() || is_home()) :
The last one worked well when I used it in my test environment. I’m not familiar enough with those functions to know how they operate, but my guess was that they were factoring in the subdirectory somehow. I honestly don’t know if that’s the case, but the above string I posted works because it operates solely based on whether the page’s number is less than one (returns ‘true’ for the index and ‘false’ for any other page).