Confluence is Atlassian's enterprise team knowledge base and document collaboration platform, founded in Sydney, Australia in 2002; with native Jira integration, a free plan for 10 users, and 1,000+ Marketplace apps.
Fleep is a team chat and project collaboration tool founded in Tallinn, Estonia in 2014, merging conversations, tasks, files and issue tracking into one thread. The free plan lets small teams start immediately.
Super Productivity is an open-source (GPL) local-first task management and time tracking app with a built-in Pomodoro timer, time tracking, and Jira integration, storing data locally by default. It is free with no subscription.
Bitbucket is a Git code-hosting and CI/CD platform founded in 2008 and now part of Atlassian, letting 10M+ users close the loop from code to deployment with unlimited private repositories and Bitbucket Pipelines, deeply integrated with the Jira ecosystem.