Results from trigonometric functions are always in RAD.
Have you activated the Complex mode? The Complex mode is indicated by a "C" in the status bar and switched off with g CF 8.
If I rapidly type a sequence of numbers, the entered keyboard number(s) are ignored. For example, if I type 123 quickly, the 2 is missed and I get 13 on the display.
While a key on the keyboard is pressed, no further key press is recognised. When you typed the 2, you had still pressed down the 1. This is exactly how the real HP-15C behaves.
Do you plan to implement other models of the Voyager series, e.g. the HP-12C?
I don't own any of the other models and I have no plans to implement them.
How can I exchange the period (decimal point) and the comma (digit separator)?
Using the mouse: Right-click the ON key or the area around the display and select "Swap comma and period".
Using the keyboard: Press Alt–. (period) or Alt–, (comma).
Where can I get a German user manual for the Simulator or the HP-15C Limited Edition?
The manual for the HP-15C Limited Edition is available only in English. However, the HP-15C LE is functionally identical to the original HP-15C from the 1980s and the Simulator. Therefore the manuals of the original HP-15C also apply to the LE and the Simulator. Copies of the original manuals are available on the CD/DVDs from the HP Calculator Museum, in French and German on CD 13 and in Portuguese on CD 15. This is the only source I know of.
I installed the HP-15C font but the Simulator keeps complaining that the font isn't installed.
This is, in my own experience, a specific problem of the KDE desktop environment. So far the problem has not been reported from other desktop environments.
The KDE font installer does not always update the font system of the underlying X-Windows system. If this happens, newly installed fonts are available for native KDE (QT) applications, but not for pure X11 applications. You have to install the font manually.
The steps to install a font manually depend on the Linux distribution you use. On many systems, namely Debian based distributions, it is sufficient to copy the font to the directory
If this does not solve the problem, please the the X.Org site about Fonts in X11R7.7
Why do some keys show a small square instead of the correct label?
Please see the Font Settings.
Do you plan to port the simulator to other operating systems like Android or iOS?
For the time being, I do not have plans to port it to other platforms.
Several commercial HP-15C emulators are available in the iOS and Andropid app stores. Of the free versions, I can highly recommend RpnCalc. I use it on all my Android devices.
Is there a configuration interface or tool to re-map the keyboard shortcuts?
There is no such thing. The keyboard shortcuts follow standards, like Ctrl–O to open a program, or are straight forward, like E for ex or S for SIN. The small number of candidates for remapping does not justify the effort.