Python アプリの実行や pip コマンドでのライブラリのインストール時にエラー

$ python3 ~/VSC/python/flask/main.py
Traceback (most recent call last):
  File "/home/mogusa/VSC/python/flask/main.py", line 1, in 
    from flask import Flask
ModuleNotFoundError: No module named 'flask'

error: externally-managed-environment
    × This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.

    If you wish to install a non-Debian-packaged Python package,
    create a virtual environment using python3 -m venv path/to/venv.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
    sure you have python3-full installed.

    If you wish to install a non-Debian packaged Python application,
    it may be easiest to use pipx install xyz, which will manage a
    virtual environment for you. Make sure you have pipx installed.

    See /usr/share/doc/python3.12/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.

sudo apt install python3-venv

python3 -m venv .python3_venv
source .python3_venv/bin/activate

deactivate