docs(frontend): update installation instructions

README.md

@@ -66,6 +66,8 @@ pip install -U pip wheel setuptools
 pip install concrete-python
 ```
 
+**Note:** Not all versions are available on PyPI. If you need a version that is not on PyPI (including nightly releases), you can install it from our package index by adding `--extra-index-url https://pypi.zama.ai`.
+
 #### Docker
 You can get the concrete-python docker image by pulling the latest docker image:
 

docs/get-started/installing.md

@@ -10,6 +10,9 @@ You can install Concrete from PyPI:
 pip install -U pip wheel setuptools
 pip install concrete-python
 ```
+{% hint style="info" %}
+Not all versions are available on PyPI. If you need a version that is not on PyPI (including nightly releases), you can install it from our package index by adding `--extra-index-url https://pypi.zama.ai`.
+{% endhint %}
 
 There are some optional features which can be enabled by installing the `full` version:
 

frontends/concrete-python/README.md

@@ -8,6 +8,8 @@ End-users should install `concrete-python` using `pip`:
 pip install concrete-python
 ```
 
+**Note:** Not all versions are available on PyPI. If you need a version that is not on PyPI (including nightly releases), you can install it from our package index by adding `--extra-index-url https://pypi.zama.ai`.
+
 ## Setup for development
 
 Developers that want to contribute to the Concrete-Python project can use the following