https://developer.garmin.com/connect-iq/core-topics/trial-apps/#apptrials
Other pages in the developer docs site will properly adjust the content to fit the width of the browser window / device screen, but the app trials page will start cutting off text once the browser viewport is narrower than ~2246px. This is especially since most people will have a viewport that's narrower than that, even on large / high-resolution screens, due to scaling.
As noted in the linked discussion, it's because of the app unlock URL example element (see screenshot in comment).
It's a <pre> element with a <code> element inside of it. Apparently the content (unlock URL) of the <code> element is so long that it's causing the <pre> element (and the rest of the page) to be too wide for most screens / resolutions, even though the <pre> element does scroll.
In the browser dev tools, if you delete the <pre> (or the <code>) element, or you edit the URL to be much shorter, the problem goes away (which proves that it's the source of the problem).