The emulator route is the way to go for me. Very happy with https://github.com/czodroid/droid48sx
There's also https://github.com/dgis/emu48android, which is technically superior in terms of features due to it's emulated system (48GX, rather than the SX)
But I'm sticking with droid48sx solely due to it's more polished user interface, and better haptic feedback when pressing the buttons. 😳
BTW, there's also HP-15C and HP-16C simulators here: https://github.com/zathras/jrpn/
Very nice! I prefer to see the stack, though, so 48SX emulator wins again. 🤓
But classic RPN calculators, revived!
Keep in mind you can also do calculations in Termux using Python or Octave, among others.
All I've mentioned are guaranteed accurate, at least.