What to use instead: open source replacements, with the gaps stated

AppFlowy is the closest open source stand-in for Notion: documents, boards and databases in one workspace, running on your own machine or server. The trade is maturity and the ecosystem around it, not the core idea.

Supabase covers the parts of Firebase most projects actually use: a database with an API in front of it, authentication, storage and realtime updates. The difference underneath is that the database is Postgres, which changes what you can do later.

There are three, and they are not interchangeable. Continue keeps the in editor experience, Aider works from the terminal against your git history, and OpenHands runs the longer autonomous job. Pick by where you want the work to happen.

The replacement is two projects rather than one. Prometheus collects and stores the metrics, Grafana shows them and alerts on them. Together they cover most of what teams use Datadog for, without the per host bill.

n8n is the practical replacement: a visual workflow builder with a large connector library that you can run yourself. Huginn is the older, more programmable option for people who would rather describe agents than draw a flow.

Syncthing replaces the syncing, not the cloud drive. Files move directly between your own machines, encrypted in transit, with no server in the middle holding a copy. If what you wanted was a backup, this is not it.

Excalidraw covers the part of Miro most people actually use: a shared canvas for diagrams and rough thinking, with a hand drawn look that keeps a sketch from reading as a decision. It is deliberately much smaller than Miro.

OpenTofu is the direct answer, because it forked from Terraform at the point the licence changed and kept compatibility as the point of the project. For most teams this is a swap rather than a migration.