nadavkav has proposed the following:

I am not a UX/UI expert, but I am not sure if this new filter input element is the proper way to filter multiple user properties.
I am working with several UX/UI experts, and will ask around to see what is the proper (best practice) way in this case, as I am sure there are several.
Until then, how about adding a static label above this special filter input field, saying something like:
"You can use the following input box to filter: Roles, eMails, Enrolment methods, ...", instead of the current "No filters applied" label.
What do you think?