Workaround for Certbot Installation on Raspbian 11 (Bullseye) armv7l with Python 3.9

Pin Dependencies to Avoid pip Install Failures

On Raspbian 11 (Bullseye) running on armv7l, installing Certbot via pip under Python 3.9 can fail due to build and dependency compatibility issues. A practical workaround is to pin versions explicitly so pip resolves a known-good combination. In particular, locking cffi to a compatible release helps prevent compilation or wheel resolution errors that block Certbot installation.

Use the following approach to proceed reliably:

pip install "cffi<2.0.0" certbot

• Pin cffi to a specific version known to work on armv7l
• Install a matching Certbot version in the same command
• Prefer a clean virtual environment to avoid conflicting packages
• Re-run with --no-cache-dir if you suspect cached artifacts
• Verify the installed versions after completion

Alternative: Install libffi-dev to Build Newer cffi

As an alternative approach, you can install the system development package for libffi so that cffi==2.0.0 can be built/installed successfully even on armv7l environments.

sudo apt update
sudo apt install -y libffi-dev
pip install "cffi==2.0.0"

If you still encounter build-related issues, also ensure basic build tooling is present (e.g., build-essential and Python headers), and retry with --no-cache-dir.

This version-pinning strategy provides a stable path to install Certbot on constrained ARM environments without changing the OS or Python version.