I have a Huawei Nova 2 with Plone 5.0.4. (Installed via termux and ubuntu core)
The issue is no horizontal scrollbar is seen.... when using firefox browser. Is this a browser constraint or a Plone UI constraint. Given the limited “screen estate” of a 5.5inch smartphone.... are there any possible solutions to navigating a page?
Usually, you should not need to scroll right or left.
In other words: the theme is not made proberly, so you should fix the theme (with CSS).
At least, you probably want this:
img { max-width: 100%; }
In some cases, you might need to scroll for example a table horizontal. On a smartphone you just 'drag the table left', but you should also consider alternative ways. (scrolling only part of the table or for example stackable (stacktable.js ) or similar