On all the Jupyter I have used, the typical OS version of the ‘Copy’ keyboard shortcut still works. On a Mac I use Command + C to copy text without needing any menu.
And if that isn’t satisfactory, there is an array of of options you can assign and or modify as keyboard shortcuts. The customization options are there. See the bottom of my reply here for an example.
Once you get in the ‘Settings Editor’ you can hit Command + f or the equivalent and bring up the search window at the bottom. Then search for the text ‘copy’ to see the options you can add or alter.