yq/pkg/yqlib/doc/headers/Sort Keys.md

The Sort Keys operator sorts maps by their keys (based on their string value). This operator does not do anything to arrays or scalars (so you can easily recursively apply it to all maps).

Sort is particularly useful for diffing two different yaml documents:

yq eval -i 'sortKeys(..)' file1.yml
yq eval -i 'sortKeys(..)' file2.yml
diff file1.yml file2.yml