Calculators, JRPN-15C and 16C, etc

Hi everyone - I’ve a recent interest in calculators which I’m pursuing. After an unfortunate experience with Droid48 (it’s hiding a chunky proprietary ROM in there without telling you clearly [shouldn’t have went near the Play Store]), I’m investigating other calculators.

What do you use? What’s the “most powerful” one which is also FOSS? I could be missing some heavyweights.

I’ve some experience with Emacs’ M-x calc, and am quite a fan, but having a portable one via the mobile phone is useful in some scenarios. I guess I’m a tad interested in the history of HP and TI machines, so was veering towards emulators of those, but they’re all proprietary it seems. HP for example seem to have the broadest selection of books - the HP48 has very cool books, which is why I was veering towards Droid48 originally.

I see that F-Droid has tons of options in any case. JRPN 16C is there, but it’s actually the “legacy” one, and for some reason the newer JRPN 15C and JRPN 16C aren’t packaged for F-Droid. What’s going on there, if anyone knows?

I should maybe mention “microMathematics Plus” too, which definitely seems serious.

Anyway, all points and experience welcome.

I know; I know; two of these are not FLOSS. I mention them here in the hope that someone knows of a FLOSS alternative.

Best overall: NeoCal from Hudren Andromeda

Best for fractions: Fraction Calculator from Digitalchemy

Simple and has a convenient widget: Fossify Calculator

Also, check this list GitHub - offa/android-foss: A list of Free and Open Source Software (FOSS) for Android – saving Freedom and Privacy..