Plain markdown pages, plus a few SilverBullet features:
Tags: ADRs, components, meetings, features, sprints and people are tagged pages, and each tag has a page that collects them, like ADR and Architecture.
Tasks and Mentions: a task in any page that mentions @hana shows up under Hana in “Who’s on what” and on her page.
Identities: everyone on the team has a person page they can be mentioned by.