LINKTOFILTEREDVIEW() can be used with a navigation action or a column type app.
You mentioned you invoke the action through a button and it works. So actions execute when invoked exclusively by the user or through workflow when certain data change condition occurs or on certain events such as form save. Please refer " When Does an Action Run?" in the article below.
In the case of starting view possibly, none of the above triggers is available to invoke the action.
Instead, you may wish to try the below.
Create a slice called say “My Planning” on the “Planning” table with a filter expression something like below
[collaborateur] = LOOKUP(useremail(), users, “email”, “user”)
Then create a ref summary view as you desire on that slice called say “My Planning”. Please set this reference view as the starting view in UX → Options