The hint suggests that Ctrl – F will not work. This suggests that the flag is either not a string object, or be exposed to client-side interface but only available in the developer tools section of the browser.
The following is the webpage listing the rules for 2023’s PicoCTF Challenge.
As predicted, the flag is an image object sneakily added to a paragraph. Whilst this can’t be located with the search shortcut, it can be found using Ctrl – F in the HTML section within developer tools on Chromium.
The alt attribute is the text that displays when image fails to load and in this case that’s the flag.