I have posted a similar question in the Expressions/Formula group with no success so I will try it here. Hopefully somebody has an answer that works otherwise PowerApps is dead to me as I have spent a ton of time trying to figure out something that should be simple.
I have created a Canvas powerapp that uses Dynamics365 as the connection. I add the phonecall entity as a datasource. All I simply want to do is show Phone calls by User so I'm attempting to Filter my datasource like this into a collection;
Do you want to filter your 'Phone Call' records based on a specific User in your app?
Based on the formula that you provided, I think there is something wrong with it. I agree with you, the 'Created By' column is a LookUp column, reference values from the Users Entity.
Within your Filter formula, the 'Created By' column is a LookUp column, but the uname variable returns a Text value, you could not compare a LookUp value with a uname variable using "=" operator (incompatible data type match).
I have made a test on my side, please consider modify your formula as below: