Yes, on version 7.1, through a built-in panel rather than by uploading anything. It is switched off by default, so having it is a decision you make rather than something that happens to you.
Switching it on
Open the SEO and AI visibility panel in your site settings.
Click SEO Settings, then the LLMS.txt tab.
Paste the file from your Fix Pack into the text field. It is written from your own pages, your own services and your own towns.
Save. Then open
yourdomain.com/llms.txtto confirm it is being served.
Squarespace says plainly that this is a proposed standard still in development, which is the same thing we say about it. Nobody is overselling this one.
If you are on 7.0
The panel is a 7.1 feature and there is no supported way to serve an arbitrary file at your root on 7.0. This check carries the smallest weight in the scan, so the honest advice is to leave it and spend the time on your structured data or your page copy instead.
Your sitemap
Generated automatically at yourdomain.com/sitemap.xml and not editable, which is fine because it does not need to be. If the finding mentions this check, it is usually the other half: page titles that repeat across pages, or missing canonical tags. Both are per-page settings under the SEO section of each page.
If your screens do not look like this, the wording has moved rather than the setting. Search your platform for the words in bold above. If you still cannot find it, send us the scan link and we will tell you where it is on your setup.