PraktiCalc
a practical calculator written in Python
...MacOS support is also here now, in form of an unsigned .app bundle. There are not that many actually useful functions provided by PraktiCalc which don't exist in a modern calculator. But you have support and integration for Linux and Windows, especially for messagebox dialog tools like zenity, kdialog and xmessage on Linux and VBS MsgBoxes on Windows. All that together with number conversion and great DPI scaling, it can be great and it will be even better in the future.