https://micro-editor.github.io/
https://github.com/zyedidia/micro
It supports modern keybindings and the mouse like a normal GUI editor.
- Shift+Arrow Keys to select text
- Ctrl+C, Ctrl+X, Ctrl+V for copy and paste operations
- Ctrl+Z for undo, Ctrl+Y for redo
- and much more...
Additionally it has support for syntax highlighting, multiple tabs, split view, is cross-platform and very easy to install (just copy the executable). This makes it perfect to use in docker environments.
P.s. It seems to be possible to run GUI apps from within docker at least on Linux (https://medium.com/@SaravSun/running-gui-applications-inside-docker-containers-83d65c0db110)