This app was mentioned in 5 comments, with an average of 2.40 upvotes
You just gave me an idea to use an RTSP app on my phone.
Onvif IP Camera Monitor (Onvifer) - for Android seems to work well and you get the RTSP stream. I can't believe I never thought of doing this.
You can enable RTSP on the cameras and use an app such as this in order to have multiple feeds playing back at the same time on Android.
Not sure if your requirement is specifically on a PC...
For android I use this app
On Windows10 I often use the Blue Iris companion or I also have two cams in a Home Assistant dashboard so I use that too
Have you tried using a generic ONVIF client app?
Something like this: https://play.google.com/store/apps/details?id=net.biyee.onvifer
This camera is used in my work, admin satisfied. ONVIF IP Camera Monitor