DuckDuckGo gets the bulk of its organic results from Bing[1], and Bing doesn’t seem to show pages from Wikivoyage[2], so contacting Bing to address that issue should fix it in DuckDuckGo, as well as any other search engines that use Bing’s index.

[1] https://help.duckduckgo.com/duckduckgo-help-pages/results/so...

[2] https://www.bing.com/search?q=wikivoyage%20malta