NocoDB is an open source Airtable alternative. It transforms your relational databases into a smart spreadsheet. Our app store allows you to connect to any cloud services like S3 for file storage and 3rd party apps like Slack, Twilio for business workflows
I love the flexibility and features of NocoDB. The fact that you can connect to an existing remote DB is a game changer, IMHO. And the fact that it's completely open source and self-hosted. I'm not a fan of the UI but I understand the use of an existing UI framework to speed up the development.