OBS Studio!

Add Source > Media Source > Name it w.e
(This will then open its properties window)

Uncheck "Local File"
Leave rest as-is

Enter RTSP Address in "Input"
(ex: RTSP://Username:[email protected]/stream1)
note: sometimes the port number may be required which is 554 default
(ex: RSTP://Username:[email protected]:554/stream1)

Save Settings and close properties window, Everything should work!

Then click "Start Virtual Camera" in the OBS Main Window