I couldn't even figure out what to do with it ! I did an extension search for "Real Media" after failing repeatedly to open a really old .rpm file from NPR.ORG , and this showed up. Of course it failed miserably.
(And yes... real player had some sort of obscure streaming protocol in .rpm extention overlapping with the other much more known .rpm Red-hat Package Manage file extension).


UPDATE:

The page with the link to that URI is: https://www.npr.org/templates/story/story.php?storyId=1072668 and the Real Media .rpm it points to is https://www.npr.org/templates/dmg/dmg_rpm.rpm?id=72668&type=1&mtype=RAM&orgId=1&p=2&story=1072668&siteplayer=true

There is some hilarious discussion on https://customer.real.com/hc/it/community/posts/360014557914-Can-t-play-RPM-file-from-NPR?mobile_site=true where an oficial Real Player representative doesn't even recognise they even had the extention , saying that .rpm is package management extension.

Turns out the actual .rpm is only a text file that points to realstream .rm/ram, and their RealServer infrastructure is probably long gone.
Then, there is also this interesting info from NPR: https://help.npr.org/customer/portal/articles/2086406-how-can-i-listen-to-older-npr-audio-that-displays-a-real-media-option-

no description what plugin this noplugin could replace. as for example what this plugin does not replace is flash or macromedia. it feels like this addon is obsolete when there is noexistent example this noplugin could replace. i havent encounter anything before trying this plugin out and i will go now without it.

Really underrated