Wikiful is described as 'online platform that makes it easy to build and share a wiki. Access and edit your wiki instantly from any device using the straightforward editor. Make wikis public or private, add collaborators, and share content effortlessly' and is a Wiki Engine in the Education & Reference category. There are more than 10 alternatives to Wikiful, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Self-Hosted solutions. The best alternative is TiddlyWiki, which is both free and Open Source. Other great sites and apps similar to Wikiful are Nuclino (Freemium), DokuWiki (Free, Open Source), Foam (Free, Open Source) and FANDOM (Free).
Nuclino is a unified workspace where teams can bring all their knowledge, docs, and projects together in one place. It’s a modern, simple, and blazingly fast way to collaborate, without the chaos of files and folders, context switching, or silos.
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.