What shared services that are available differs from system to system, just like which are supported differ from applucation to application. Filesystem access m

What shared services that are available differs from system to system, just like which are supported differ from applucation to application. Filesystem access may be through an xdg-portal, may support KIO or GVFS integrations, may use framework internal pickers, and so forth. Many decisions for the developers to make. Filesystem drivers are much further down the stack, but that's just a different group of developers making all the decisions.