My personal favorite is DokuWiki - https://www.dokuwiki.org/ https://www.dokuwiki.org/ Flat files so very easy to make backups, it's got your standard wiki fun

My personal favorite is DokuWiki - https://www.dokuwiki.org/ https://www.dokuwiki.org/ Flat files so very easy to make backups, it's got your standard wiki functionality (revision history and all that good stuff) and has a fair few community-made extenions too Edit: To address another comment here - it also has search functionality