How to query WFS layer in ArcGIS Online?

I want to incorporate the following WFS query URL in ArcGIS Online:

https://9.9.9.9:8080/geoserver/workspace/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=workspace:education&filter=
<PropertyIsEqualTo><PropertyName>amenity</PropertyName>
<Literal>school</Literal></PropertyIsEqualTo>

The query above was tested positively. However when adding that to ArcGIS Online the URL requires to be shortened down to ‘GetFeature’, the layer selection happens via dropdown menu and supposedly the query part goes into ‘Add Parameters’ doesn’t it?

Parameter = filter
Value = <PropertyIsEqualTo><PropertyName>amenity</PropertyName>
    <Literal>school</Literal></PropertyIsEqualTo>

I also tried to add the workspace/layer declaration as parameter to no avail. The Parameters appear to be ignored because all the GML is parsed unfiltered.
What am I missing here?

Note: The answer here suggests to tediously sign up to an ESRI developer account but that seems to be from a time where WFS wasen’t supported at all.