One question that often arises about having a two website for mobile and desktop (just like Duda does) is the issue of duplicate content. When search engines crawl your desktop site and mobile site, they take note of your content. If they see duplicate content, they assume you are trying to cheat the system in order to get ahead in the rankings. Since having two different websites is a completely accepted way of going mobile, a link tag was created to get around the duplicate content issue. The good news is that Duda adds this tag automatically to each and every page.
The exact tag is the rel="canonical" tag, which tells search engines that this page on mobile is related to this page on desktop, as to not see it as duplicate content. Here's the canonical tag, as an example, that Duda added automatically.
If you want to read up a bit more on the canonical link tag, take a look at this great article by Google.