Power Apps portals: Start using code components with portals (Preview)
In this release the feature provides support for Field type of code components allowing fields on portal forms to be replaced with code components.
The configuration for field type of components remains largely same as how you’d configure a code component for model-driven app form and then use that form definition within your portal via entity or web forms.
Below is an overview of the 3 step process to give you an idea
Documentation is available here – Use code components in portals (Preview) and you can try this capability via – Tutorial: Use code components in portals (Preview)