Flutter but the range of supported deployment target versions is 10.9 to 12.3.99. (in target 'FMDB' from project 'Pods')

The error message you're seeing is indicating that the deployment target for macOS that is set in your FMDB Pod is lower than the minimum supported version. The minimum supported version for your configuration is 10.9, but your Pod is set to target 10.6.

There are a few ways you could resolve this issue.

Update the Podfile: You could try updating the Podfile to explicitly set the platform for macOS to a later version. This can be done by adding the following line at the top of your Podfile:
```
platform :osx, '10.9'
```
After adding that line, run pod install to update your Pods.
Manually set the deployment target in Xcode: Open the .xcodeproj file in Xcode, select the FMDB target in the project navigator, then go to the Build Settings tab. Find the "Deployment Target" setting and set it to at least 10.9.
Update the Pod: If the FMDB Pod has been updated to support later versions of macOS, you could try updating the Pod to the latest version. This can be done by running the following command in your terminal:
```
pod update FMDB
```

Remember, before making any changes it's a good idea to commit your current working version to version control (like git), so you can easily revert back if something goes wrong.