Using manual SharePoint fill-in choice values in your PowerApp

 If you’re using a SharePoint choice field you can set the ‘Allow fill-in choices‘ 

First, you need to make sure the ‘Allow searching‘ option is enabled (which is by Default) on the choice field in your PowerApp by selecting your dropdown control and enabling Allow searching in the Properties pane

With that option enabled, users are able to search the drop-down by entering a value which will search for that specific value. Since your have user input with this option, you can also use this to store that value into your list item. You can achieve this by adding the following function to the Update() property of your DataCard:

If(

    !IsBlank(DataCardValue10.Selected),

    DataCardValue10.Selected,

    If(

        !IsBlank(DataCardValue10.SearchText),

        {

            Value: DataCardValue10.SearchText,

            '@odata.type': "#Microsoft.Azure.Connectors.SharePoint.SPListExpandedReference"

        },

        Blank()

    )

)

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