qtbase5-dev is already the newest version

If "qtbase5-dev" is already installed and up to date, but you are still encountering the unmet dependencies error, you can try the following steps to resolve the issue:

1. Remove conflicting packages: Run the following command to remove any conflicting packages:

   sudo apt-get remove qt5-default

2. Clean package cache: Clear the package cache to ensure you have the latest package information:

   sudo apt-get clean

3. Update package lists and upgrade packages: Update the package lists and upgrade all installed packages using the following commands:

   sudo apt-get update
   sudo apt-get upgrade

4. Reinstall the desired package: Finally, reinstall the package you initially wanted to install:

   sudo apt-get install qt5-default

These steps should help resolve the unmet dependencies issue related to the "qt5-default" package. If you still encounter any problems, please provide more information about your system setup and any error messages you receive for further assistance.