I use TiddlyWiki (https://tiddlywiki.com). It's brilliantly simple to set up (doesn't require a database for example), has a small but nice plugin ecosystem with things like Markdown support, etc.
I'm not currently using a personal wiki, but both MediaWiki and Confluence are pretty easy to set up. Confluence/Jira licenses are cheap for self-hosted personal use. MediaWiki is oss and probably not going anywhere anytime soon.