and another attempt

.readthedocs.yaml

@@ -9,5 +9,5 @@ sphinx:
   configuration: docs/conf.py
 python:
   install:
-    - method: pip
+    - requirements: docs/requirements.txt
-      path: sphinx-rtd-theme
+    

docs/requirements.txt

@@ -0,0 +1 @@
+sphinx-rtd-theme