For DOS TUI, the standard was https://en.wikipedia.org/wiki/IBM_Common_User_Access: Shift+Delete to cut, Ctrl+Insert to copy, Shift+Insert to paste. These worked in DOS utilities like EDIT.COM, QBASIC.EXE and HELP.EXE, in all Turbo Vision apps including Borland Pascal and Borland C++ IDEs, in Visual Basic and Visual FoxPro for DOS, and they still work today in any Windows app that doesn't try to play silly tricks with its UI by doing its own text input.
Shift+Insert has worked for decades in the XTerms I've used. It's bound in my muscle memory and is a source of frustration, for me, when attempting to use non-X Widows GUIs or odd-ball "terminals"/programs/foo.
