Stubia is described as 'mobile encyclopedia that limits each article to 160 characters: this limitation makes each topic easy to understand' and is an website in the Education & Reference category. There are more than 25 alternatives to Stubia, not only websites but also apps for a variety of platforms, including Android, iPhone, iPad and Android Tablet. The best alternative is Wikipedia, which is both free and Open Source. Other great sites and apps similar to Stubia are FANDOM (Free), Miraheze (Free, Open Source), Encyclopædia Britannica (Freemium) and WikiSpooks.com (Free, Open Source).
Wikipedia is a free, multilingual encyclopedia project supported by the non-profit Wikimedia Foundation. Wikipedia has 17 million articles (3.5 million in English), which have been written collaboratively by volunteers around the world.
Miraheze is a free wiki farm, you can request your wiki which is 100% free and has no ads. The code of Miraheze is opensource (Github.com/Miraheze). You can change your logo, request extensions you need, and many other features. Help is provided via email, IRC, Phabricator.
WikiSpooks is a global alternative encyclopedia on politics, spy craft, deep state intelligence, and conspiracies, free of corporate influence, partisan politics, or government propaganda for historians and truth-seekers to read, edit, and share.
Reference.com offers a massive online dictionary, thesaurus, encyclopedia, quote finder, and translator (powered by Google Translate)- all for free. For the Dictionary.com and Thesaurus.com mobile app, go here. Dictionary.com
Welcome to WikiIndex, a wiki of all wiki, wiki people, wiki software, wiki farms, and wiki ideas, a 'work in progress' founded in 2006. This is part of a continued effort to self-organize information collaboratively, started by Ward Cunningham a decade ago.
Citizendium, powered by MediaWiki, is "an open wiki project dedicated to creating a free, comprehensive, and reliable repository of structured knowledge". Unlike with Wikipedia, a contributor must register using their real name and verify their identity.