HI André Cecílio,
Put a datview In the pageB where you are going to show Filterered list.
The data View will have the object EnitityA and inisde the data view you can either put a List view or Data drid and Select Microflow as Datasource, now the Datasource microflow (FDS_Filterlist) will have a paremeter of entity A and now do your filter operation and return the list.
Now Call page B from the card Action.
Hope this will work.
For Duplicate values you can add a microflow and create a New List for Entity A and iterate iterate View list and check if this value is present( based on a primary key) in New list created outisde the loop, if present conitue in the loop if not add int he new list and at the end of the micrflow return the new list.
Kindly accept if the solution works for you.