This QR Code library supports decoding a QR Code image.
$ dotnet add package QRCodeDecoderUse this to decode a QR Code to data or a string.
...
services.AddQRCodeDecoder();
...
var decoder = _serviceProvider.GetRequiredService<QRDecoder>();
byte[][] data = decoder.ImageDecoder(sourceBitmap);
var data = QRDecoder.ByteArrayToString(data[0]);