Here is the full set of steps that solved the problem for me:

# Delete old build artifacts

rm -rf build

rm -rf ios/build

# Regenerate iOS-related files

flutter precache --ios

flutter pub get

# Rebuild (codesigning disabled)

flutter build ios --no-codesign

Eventually I discovered that the project could successfully build in Android Studio, and after that Xcode was also able to build it without errors.