About two years have passed since: https://www.telerik.com/forums/decrypting-tls-1-3
It looks like .NET supports TLS1.3 as of now. At least on Windows 11 TLS1.3 is enabled out of the box. Will Fiddler Classic support TLS 1.3 ? Will it get new features in general or is Fiddler Everywhere where most of development happens nowadays?
This forum is entirely dedicated to Fiddler Everywhere so that said FIddler Everywhere will support TLS 1.3 in a future release. That will most likely happen when an official version of Windows 11 is released (as currently Microsoft are not planning on supporting TLS 1.3 in Windows 10) https://docs.microsoft.com/en-us/windows/win32/secauthn/protocols-in-tls-ssl--schannel-ssp- ) .
For requesting and discussing possible Fiddler Classic features please use the Fiddler feedback portal.