Usage example Rates is a scriptable CLI tool that brings currency exchange rates right into your terminal and supports 30+ fiat and 10K+ crypto currencies.
Alacritty is a modern terminal emulator that comes with sensible defaults, but allows for extensive configuration. By integrating with other applications, rather than reimplementing their functionality, it manages to provide a flexible set of features with high performance. The supported platforms currently consist of BSD, Linux, macOS and Windows.
The initial load of categories takes a bit longer than the second load and the app looks non-responsive. I actually cancelled running it and took a look at the source to understand the reason for the delay before noting this.