Units-converter widget in MacBook Pro

This third-party article tells where they went in Catalina (to the Today tab under Notifications) , how to get more, and where they are headed for BigSur:

https://www.macworld.co.uk/how-to/mac-software/use-widgets-mac-3794391/

That was available as a widget under Dashboard. It's still there under Mojave.

Other Readers will have to fill us all in about where it went under Catalina.

This is part of the internal convergence of software for iPhone, iPad, and Mac. Apple Silicon will be pushing even harder on convergence is future.

OOH, that is good information about Units-converter inside Calculator.app -- the Stand-alone Application.

Adding Calculator to the TODAY view seems to give you ONLY the four-function calculator, and I can not figure out how to even get a square root key, much less scientific presentation or any trace of Units-Converter.