Update ambient install docs to specify Python version

src/install.rst

@@ -213,7 +213,9 @@ Set up a Nextstrain runtime
 
       The ambient runtime does not require a particular setup method; it will work as long as the programs you wish to use are available.
 
-      The following describes how to accomplish this using a custom Conda environment as an example. You should be familiar with the `basics of Conda <https://conda.io/projects/conda/en/latest/user-guide/getting-started.html>`__ before proceeding.
+      .. Suggest Python ≤3.10 because Augur on Bioconda won't resolve dependencies on Python ≥3.11: <https://github.com/nextstrain/augur/issues/1334>
+
+      The following describes how to accomplish this by creating a new custom Conda environment, as an example. You should be familiar with the `basics of Conda <https://conda.io/projects/conda/en/latest/user-guide/getting-started.html>`__ before proceeding. If you want to add Nextstrain to an existing Conda environment, please make sure you're using Python ≤3.10 and activate that environment instead of creating a new one.
 
       .. tabs::
 

src/snippets/ambient-setup.rst

@@ -1,19 +1,20 @@
-1. Activate a Conda environment that you wish to use:
+1. Create a new Conda environment and install all the necessary software:
 
    .. code-block:: bash
 
-      conda activate <your-environment-name>
-
-2. Install all the necessary software:
-
-   .. code-block:: bash
-
-      conda install --override-channels --strict-channel-priority \
+      conda create -n <your-environment-name> \
+            --override-channels --strict-channel-priority \
             -c conda-forge -c bioconda --yes \
             augur auspice nextclade \
             snakemake git epiweeks pangolin pangolearn \
             ncbi-datasets-cli csvtk seqkit tsv-utils
 
+2. Activate the runtime:
+
+   .. code-block:: bash
+
+      conda activate <your-environment-name>
+
 3. Set the runtime:
 
    .. code-block:: none