When setting the survey have a look at the 'presentation' tab...You can easily change the template.
FYI, LS use HTML4 standard (doctype =>XHTML 1.0 Transitional) and it's not only a 'template' affaire.... Doctype declaration is not included in the template but in a core file.
All in all this does not change anything concerning the features or display, included for mobile devices... because LS doesn't use new pure HTML5 (forms) elements.
If you have to adapt a template, just use CSS media queries...and your survey will render very welll with any kind of (small) device
For more resources about this topic, you may have a look
here
Ben/