Some templates are ending up in GEOSERVER_DATA_DIR/templates/ogc/stac/ but should be going to GEOSERVER_DATA_DIR/templates/ogc/stac/v1/
For the most part that seems to be true but there was a client report of a few issues with stac templates. Hopefully this will address that.
I think both locations may be valid. I tried to make template location handling consistent in a previous fix for OGCAPI
Some templates are ending up in GEOSERVER_DATA_DIR/templates/ogc/stac/ but should be going to GEOSERVER_DATA_DIR/templates/ogc/stac/v1/