I'm sure most folks are aware of the list on Are we Wayland yet?, which has a lot of great apps. Most of the standard desktop ones are already included with Manjaro Sway edition. However, one glaring omission was a calculator app (bc is of course included and usable on the terminal, but can be rather cumbersome for complex calculations).
Today, I stumbled across a very nice alternative: speedcrunch. So far it's been working great natively on Sway thanks to being based on the latest qt5-tools. Nice fast keyboard-based interface with the option to use a GUI keypad, binary ("Bitfield") input, support for expressions, functions, mathematical constants, smart completion, complex numbers, and more!
Really much happier with this app when compared to the more basic gnome-calculator, and even GNU bc ("basic calculator" or "bash calc" as I like to call it).