Baserow

Baserow is a self-hosted open-source database combining a spreadsheet interface with automatic REST API generation. You can run it on your own infrastructure, build relational schemas visually, and invite teams to collaborate in real time without any backend coding.

It's ideal for teams that want Airtable-like features but need self-hosting or a lower cost structure. The plugin system lets you extend with custom integrations, and the open codebase means you can inspect and modify everything to fit your specific needs.