Here's a concise step-by-step guide to download, verify the hash, and set up Conda on your Debian 12 system:

1. Update your system:
   ```
   sudo apt update && sudo apt upgrade
   ```

2. Install required dependencies:
   ```
   sudo apt install wget gpg python3 python3-pip
   ```

3. Download the Miniconda installer:
   ```
   cd ~/Downloads
   wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh
   ```

4. Verify the hash of the downloaded installer:
   ```
   wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh.sha256
   sha256sum Miniconda3-latest-Linux-x86_64.sh
   cat Miniconda3-latest-Linux-x86_64.sh.sha256
   ```

5. Install Miniconda:
   ```
   chmod +x Miniconda3-latest-Linux-x86_64.sh
   ./Miniconda3-latest-Linux-x86_64.sh
   ```

6. Initialize Conda:
   ```
   source ~/.bashrc
   conda --version
   conda init bash
   ```

7. Create a Conda environment:
   ```
   conda create --name myenv python=3.12
   conda activate myenv
   ```

8. Update pip and install packages within the environment:
   ```
   python3 -m pip install --upgrade pip
   python3 -m pip install jupyter numpy pandas matplotlib
   ```

9. Launch Jupyter Notebook from the active environment:
   ```
   jupyter notebook
   ```

10. Deactivate the environment when done:
    ```
    conda deactivate
    ```

Remember to replace `myenv` with your desired environment name and adjust the Python version and package list according to your requirements.