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Plaintext and a simple kanban board are all you need.
I've been using one called Planka and it's great. Incredibly minimal and all important info is documented elsewhere so it can just be used for organization.
Love using a basic SQL database for data warehousing (we need it for billing purposes and SQL records give us a lot more freedom to set up visualizations and data dashboards).
All day to day communication is either in person, over chats, or though plaintext files and comments left in project directories.