You can build a QR-based contact system by using a backend that acts as a bridge between the user and the vehicle owner, without revealing personal details.
Basic flow:
Generate a unique ID for each user
Store user contact details securely in a database
Create a QR code containing that unique ID
When someone scans the QR:
Redirect to a web page
Provide a form (message/call request)
Send notification to the owner via API (SMS/email)
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