It’s best practice to start attribute names with an uppercase character in Mendix.
https://docs.mendix.com/howto/general/dev-best-practices#3-2-2-entity-attributes
If you do want to lowercase them, then I think it is a manual process unless you are happy to use the Mendix SDK and write some Typescript to change them programatically.
https://docs.mendix.com/apidocs-mxsdk/mxsdk/changing-things-in-the-model
Really against the common used best practices in Mendix development. As using Camel/pascal case naming of entities and attributes helps a lot in Mendix development