Last year Microsoft open sources the modern Windows 10 Calculator and today the app showed up on Linux, courtesy of the Uno Platform.
The Uno Platform is a cross-platform runtime for C# and XALM and like Java is supposed to make cross-platform apps look native on any supported platform.
On Linux, the Uno Platform apps make use of the Skia rendering engine to draw the UI and integrate into the Ubuntu desktop with a regular GTK frame and is built using the Mono Project.
The calculator has been uploaded to the Snap Store as Uno Calculator, to avoid copyright issues, and supports standard, scientific, and programmer calculator functionality, as well as a set of converters between various units of measurement and currencies.
OMGUbuntu notes that it is better than the native Gnome calculator, mainly due to supporting more conversions, and stands as a good proof of concept for the Uno Project.
The app can be found in the Snap Store here.