To be honest, I mostly use a physical calculator (Swissmicros DM41L, which is an HP41CX clone). Second choice is the i41CX+ app on my phone. The HP41 keyboard and operational patterns were etched into my brain at university, since my first engineering calculator was an HP41C.
Not sure what the parent uses, but emacs has calc, which is a RPN calculator with lots of features (including history and intermediate results) and can be used in the terminal
I have used rpncalc and T_REX (https://isene.org/2021/02/T-REX.html) in the terminal, dc or gforth in a pinch.