diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 3bb0bdea0..13d2f39e4 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -79,6 +79,10 @@ jobs:
           environment-file: devtools/conda-envs/${{ env.ENVFILE }}.yaml
           create-args: >-
             python=${{ matrix.python-version }}
+          # default - will pull down 2.0 which we don't want!
+          # micromamba-version: latest
+          # pin to latest 1.x release
+          micromamba-version: "1.5.10-0"
 
       - name: Make oe_license.txt file from GH org secret "OE_LICENSE"
         env:
diff --git a/.github/workflows/beta_rc.yaml b/.github/workflows/beta_rc.yaml
index 48a308ef1..222abe9ac 100644
--- a/.github/workflows/beta_rc.yaml
+++ b/.github/workflows/beta_rc.yaml
@@ -44,6 +44,10 @@ jobs:
               - conda-forge
           create-args: >-
             python=${{ matrix.python-version }}
+          # default - will pull down 2.0 which we don't want!
+          # micromamba-version: latest
+          # pin to latest 1.x release
+          micromamba-version: "1.5.10-0"
 
       - name: Make oe_license.txt file from GH org secret "OE_LICENSE"
         env:
diff --git a/.github/workflows/conda.yml b/.github/workflows/conda.yml
index 8c426241f..666ac5d3a 100644
--- a/.github/workflows/conda.yml
+++ b/.github/workflows/conda.yml
@@ -48,6 +48,10 @@ jobs:
           environment-file: devtools/conda-envs/conda_oe.yaml
           create-args: >-
             python=${{ matrix.python-version }}
+          # default - will pull down 2.0 which we don't want!
+          # micromamba-version: latest
+          # pin to latest 1.x release
+          micromamba-version: "1.5.10-0"
 
       - name: Additional info about the build
         run: |
@@ -126,4 +130,4 @@ jobs:
 
       - name: Run example notebooks
         run: |
-          python -m pytest -r fE -v -x --tb=short --nbval-lax --ignore=examples/deprecated examples
\ No newline at end of file
+          python -m pytest -r fE -v -x --tb=short --nbval-lax --ignore=examples/deprecated examples
diff --git a/.github/workflows/examples.yml b/.github/workflows/examples.yml
index 108f3dc93..bf415296b 100644
--- a/.github/workflows/examples.yml
+++ b/.github/workflows/examples.yml
@@ -65,6 +65,10 @@ jobs:
           environment-file: devtools/conda-envs/${{env.ENVFILE}}-examples.yaml
           create-args: >-
             python=${{ matrix.python-version }}
+          # default - will pull down 2.0 which we don't want!
+          # micromamba-version: latest
+          # pin to latest 1.x release
+          micromamba-version: "1.5.10-0"
 
       - name: Additional info about the build
         run: |
diff --git a/.github/workflows/installer.yml b/.github/workflows/installer.yml
index 38937b0d8..bb2388655 100644
--- a/.github/workflows/installer.yml
+++ b/.github/workflows/installer.yml
@@ -20,92 +20,95 @@ jobs:
       PYVER: ${{ matrix.python-version }}
 
     steps:
-    - uses: actions/checkout@v4
-
-    - name: Install conda environment
-      uses: mamba-org/setup-micromamba@v1
-      with:
-        environment-file: devtools/conda-envs/installer.yaml
-        create-args: >-
-          python=${{ matrix.python-version }}
-
-    - name: Additional info about the build
-      shell: bash
-      run: |
-        uname -a
-        df -h
-        ulimit -a
-
-    - name: Environment Information
-      shell: bash -l {0}
-      run: |
-        conda info
-        conda list
-
-    - name: Prepare and run the constructor
-      shell: bash -l {0}
-      run: |
-        #cd ..
-
-        # Find the tag of the last release (excluding RCs)
-        # TODO: Make this a variable that can be passed through from trigger and/or allow RC
-        export LATEST_TAG=$(git ls-remote --tags https://github.com/openforcefield/openff-toolkit.git | cut -f2 | grep -E "([0-9]+)\.([0-9]+)\.([0-9]+)$" | sort --version-sort | tail -1 | sed 's/refs\/tags\///')
-
-        echo $LATEST_TAG
-
-        git clone https://github.com/openforcefield/toolkit-installer-constructor
-        cd toolkit-installer-constructor
-
-        python ../devtools/scripts/build_cookiecutter_json.py $LATEST_TAG $PYVER $CI_OS
-        cp new_cookiecutter.json cookiecutter/cookiecutter.json
-
-        cat new_cookiecutter.json
-
-        python run.py
-
-        pwd
-        ls
-        ls build
-
-    - name: Upload installer as artifact
-      uses: actions/upload-artifact@v4
-      with:
-        name: ${{ matrix.os }}_py${{ matrix.python-version }}.sh
-        path: toolkit-installer-constructor/build/openff-toolkit*/openff-toolkit*.sh
-
-    - name: Install from installer
-      shell: bash -l {0}
-      run: |
-        #cd ..
-        pwd
-        ls
-        ls toolkit-installer-constructor
-        ls toolkit-installer-constructor/build
-        ls toolkit-installer-constructor/build/openff-toolkit-*/
-
-        mkdir scratch
-        cd scratch
-        echo $HOME/constructor_install/ | bash ../toolkit-installer-constructor/build/openff-toolkit-*/openff-toolkit-*.sh
-
-        conda activate $HOME/constructor_install/
-        conda info
-        conda list
-
-        export FOUND_VER=$(python -c "import openff.toolkit; print(openff.toolkit.__version__)")
-        export LATEST_TAG=$(git ls-remote --tags https://github.com/openforcefield/openff-toolkit.git | cut -f2 | grep -v "rc" | tail -1 | sed 's/refs\/tags\///')
-
-        echo $LATEST_TAG
-        echo $FOUND_VER
-
-        if [[ $LATEST_TAG != $FOUND_VER ]];
-          then echo "Version mismatch"
-          exit 1
-        fi
-
-        PYTEST_ARGS=" -r fE --tb=short"
-        PYTEST_ARGS+=" --ignore=openff/toolkit/_tests/test_links.py"
-
-        # This should work if run directly at release time, but a safer approach would be
-        # to `git checkout` the corresponding tag of the release, see PR #577
-        pytest $PYTEST_ARGS ../
-
+      - uses: actions/checkout@v4
+
+      - name: Install conda environment
+        uses: mamba-org/setup-micromamba@v1
+        with:
+          environment-file: devtools/conda-envs/installer.yaml
+          create-args: >-
+            python=${{ matrix.python-version }}
+          # default - will pull down 2.0 which we don't want!
+          # micromamba-version: latest
+          # pin to latest 1.x release
+          micromamba-version: "1.5.10-0"
+
+      - name: Additional info about the build
+        shell: bash
+        run: |
+          uname -a
+          df -h
+          ulimit -a
+
+      - name: Environment Information
+        shell: bash -l {0}
+        run: |
+          conda info
+          conda list
+
+      - name: Prepare and run the constructor
+        shell: bash -l {0}
+        run: |
+          #cd ..
+
+          # Find the tag of the last release (excluding RCs)
+          # TODO: Make this a variable that can be passed through from trigger and/or allow RC
+          export LATEST_TAG=$(git ls-remote --tags https://github.com/openforcefield/openff-toolkit.git | cut -f2 | grep -E "([0-9]+)\.([0-9]+)\.([0-9]+)$" | sort --version-sort | tail -1 | sed 's/refs\/tags\///')
+
+          echo $LATEST_TAG
+
+          git clone https://github.com/openforcefield/toolkit-installer-constructor
+          cd toolkit-installer-constructor
+
+          python ../devtools/scripts/build_cookiecutter_json.py $LATEST_TAG $PYVER $CI_OS
+          cp new_cookiecutter.json cookiecutter/cookiecutter.json
+
+          cat new_cookiecutter.json
+
+          python run.py
+
+          pwd
+          ls
+          ls build
+
+      - name: Upload installer as artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.os }}_py${{ matrix.python-version }}.sh
+          path: toolkit-installer-constructor/build/openff-toolkit*/openff-toolkit*.sh
+
+      - name: Install from installer
+        shell: bash -l {0}
+        run: |
+          #cd ..
+          pwd
+          ls
+          ls toolkit-installer-constructor
+          ls toolkit-installer-constructor/build
+          ls toolkit-installer-constructor/build/openff-toolkit-*/
+
+          mkdir scratch
+          cd scratch
+          echo $HOME/constructor_install/ | bash ../toolkit-installer-constructor/build/openff-toolkit-*/openff-toolkit-*.sh
+
+          conda activate $HOME/constructor_install/
+          conda info
+          conda list
+
+          export FOUND_VER=$(python -c "import openff.toolkit; print(openff.toolkit.__version__)")
+          export LATEST_TAG=$(git ls-remote --tags https://github.com/openforcefield/openff-toolkit.git | cut -f2 | grep -v "rc" | tail -1 | sed 's/refs\/tags\///')
+
+          echo $LATEST_TAG
+          echo $FOUND_VER
+
+          if [[ $LATEST_TAG != $FOUND_VER ]];
+            then echo "Version mismatch"
+            exit 1
+          fi
+
+          PYTEST_ARGS=" -r fE --tb=short"
+          PYTEST_ARGS+=" --ignore=openff/toolkit/_tests/test_links.py"
+
+          # This should work if run directly at release time, but a safer approach would be
+          # to `git checkout` the corresponding tag of the release, see PR #577
+          pytest $PYTEST_ARGS ../