yes sure I did it.
I installed Fiddler app on my PC. I also have two mobile phones (one with Android v5, another with Android v8).
I installed the same certificate for both phones. And I set the same proxy settings to them.
I can see all requests for the phone with Android v5.
But I don't see requests for the phone with Android v8. There are only 'Tunnel to' connections.
It seems I found the answer for this problem:
"In Android 7 all apps that target API Level 24 and later will ignore all user-installed root certificates by default. I cannot find information if this changed in Android 8 so I assume it is still valid. Only app developers can override this behavior for their app only and from what I'm reading the app you are trying to debug is yours. You can find more information about how to do it here."
Does it mean I cannot use Fiddler with Android 7 and higher?