1) Certificates generated using Fiddler.DefaultCertificateProvider
2) I'm capturing traffic from my company's apps, which are only available on french store. I'v tried with two of them (allociné, jeuxvideo.com), both failing with fiddler 4.6.10 and both succeeding on earlier builds.
I use fiddler to read the google analytics batch messages. I guess that you could replicate my issue with any app that is using GA SDK. I'v tried with several different Android devices and they all failed with fiddler 126.96.36.199
3) It still works on our iOS apps. I haven't tried my desktop browser because I don't need this feature, let me know if you think it could make a difference (I've setup fiddler to only work with remote clients so I'd rather not change this setup unless it's really necessary).
To be more precise, I do see the "tunnel to" line, but I'm missing the second line which actually contains the whole thing.
I hope those information can help you work this out ! If not, let me know and I'll do my best to assist you.