@swinnings
As with any datasource, PowerApps will infer the data types of the columns based on conditions. For SharePoint, it basically looks at the column datatype. For Excel, it has to infer the type based on the data and formatting of that column in the spreadsheet.
AND, just like any datasource, you cannot change the datatype that PowerApps inferred directly in the app itself, you have to change it in the datasource.
So, for Excel, the trick will be to get PowerApps to infer the data type that you want. For example, if you had a date coming in and you wanted text, then you would have to alter the column formatting in Excel to convert the date values into text there.
I hope this is helpful for you.
