Can I override 404 pages?

Is it possible to have customized error pages for fat-fingered user entered URLs? Which xml files would have to override in order to catch 404 in these 2 conditions:

Assume that kcIP kcPort gcIP and gcPort are the actual ip:port properly functioning and xyz is a mistyped “auth” or “oauth” accordingly

keycloak: https://kcIP:kcPort/xyz
I receive the following page back: “404 - Not Found

I was hoping that overriding themes/base/admin/resources/partials/pagenotfound.html would do the trick but not.

I receive the following page back:
"Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Mon Mar 16 21:03:09 GMT 2020
There was an unexpected error (type=Not Found, status=404).
No message available"



Any ideas anyone ? Thanks!