I do not see a link next to "Include Symbols'...I was able to download the files using an instruction provided by flutter.
https://firebase.google.com/docs/crashlytics/get-deobfuscated-reports?platform=ios&authuser=1
Run the following to display all your dSYMs' UUIDs on your machine, then search for the missing dSYM:
mdfind -name .dSYM | while read -r line; do dwarfdump -u "$line"; done
Once you find the dSYM, upload it to Crashlytics. If the mdfind command doesn’t return any results, you can look in the Products directory where your .app lives (by default, the Products directory is located in Derived Data). If your app is released to production, you can also look for its dSYM in the .xcarchive directory on disk:
In Xcode, open the Organizer window and select your app from the list. Xcode displays a list of archives for your project.
Control-click an archive to view it in Finder. Then, control-click it again and click Show Package Contents.
Within .xcarchive is a dSYMs directory that contains dSYMs generated as part of Xcode’s archiving process. Recompiled bitcode dSYMs are also downloaded to this folder when you use the Download dSYMs... tool in the Organizer window.