IMO MkDocs Material is very easy to set up and customize. Use Docusaurus if you need a lot of customization. Both of these have built-in search and output static websites.
MkDocs Material is sponsorware, though. If you need the "blog" feature you'll need to cough up $15. Docusaurus is from Meta and is fully free.
Zendesk: Zendesk is a customer service platform that includes a knowledge base feature. The knowledge base allows you to create and organize articles, tutorials, and other content to help users find answers to their questions.
Help Scout: Help Scout is a customer support platform that includes a knowledge base feature. The knowledge base allows you to create and organize articles, tutorials, and other content to help users find answers to their questions.
DocuSign: DocuSign is a document management platform that includes a document library feature. The document library allows you to upload and organize documents, such as user guides and tutorials, for easy access by customers.
Confluence: Confluence is a team collaboration platform that includes a knowledge base feature. The knowledge base allows you to create and organize articles, tutorials, and other content to help users find answers to their questions.
Google Docs: Google Docs is a cloud-based document management platform that includes collaboration features. You can create and share user guides and tutorials with customers, and allow them to comment and ask questions directly within the document.
The structure described there helps people avoid creating docs that mix the different use cases we all have for seeking out documentation.