If you use sap.ui.model.odata.v2.ODataModel you can do clientside filtering while online as well.
To do so, change the OperationMode to a different mode while initialising the model. For the options see the sap.ui.model.odata.OperationMode in the API docs of UI5.
But as that model works a bit different I don't know if it is fully compatible with the offline store.
Found an outstanding issue in the OpenUI5 git at least: odata.v2.ODataModel, Kapsel OData Offline, DataBinding · Issue #504 · SAP/openui5 · GitHub