Oracle 18c 10.7.1 EGDB:
This isn't my area of expertise; I'm posting this idea because it's an issue my organization dealt with recently. I'll try to explain it as well as I can.
We can apply an arcade expression to a field in the identify window.
return Replace($feature["FILE_URL"]," ","%20")
But that expression doesn't get applied to the fields in the attribute table widget.
Related: Hyperlink Field — Replace spaces with URL-encoded value “%20”
Could web maps be enhanced so that arcade expressions apply to the attribute table widget?