Please allow filtering of uploaded files in AGOL. Currently in AGOL, you can upload .csv and .txt files directly to a web map and interact with the data in a variety of ways, such as changing symbology, classifying data, creating labels, etc., but filtering your table in an uploaded file is not supported functionality.
According to Esri: You can create filters on hosted feature layers, ArcGIS Server feature service layers, and ArcGIS Server map service layers that have associated attribute data. You cannot create filters on map notes or features imported from a file.
It is understood that hosting your data in either the Esri cloud or your local ArcGIS for Server environment is the preferred/superior way to share your geospatial data with the online community, but there are also times when it may be impractical to do so.