LimeSurvey version: 6.1.8
Own server or LimeSurvey hosting: Own server
==================
I would like to change the very first page when going onto the limesurvey page. For more detail, it is the page that states "The following surveys are available." I am unable to locate the files that create the page, so therefore I am unable to change them. Is this something that can be done, and, if so, how would I go about doing it?

Search for survey list in the theme files.

As you didn't say which survey theme you are using, we can't give more specific details.

For the Index page with the survey list the chosen default theme is used.