algorithm2e does not set \texttt

By default, algorithm2e uses \ProgSty for that part, which is defined to use \emph.

It also provides \SetProgSty to modify the output (with a peculiar syntax), but does the wrong thing, because it turns out that \SetProgSty changes \ArgSty.

You can fix it and do the required setting.

Note that algorithmic and algorithm2e aren't compatible. Use either, but not both.

\documentclass{article}
\usepackage[german, linesnumbered, boxruled]{algorithm2e}
%\usepackage{algorithmic}

%%% fix a bug in algorithm2e
\renewcommand{\SetProgSty}[1]{%
  \renewcommand{\ProgSty}[1]{% <--- algorithm2e.sty has \ArgSty
    \textnormal{\csname#1\endcsname{##1}}\unskip
  }%
}

\newcommand{\pythonsyntax}{%
    \SetStartEndCondition{ }{}{}%
    \SetKwProg{Fn}{Funktion}{:}{End}%
    \SetKwFunction{Range}{range}%%
    \SetKw{KwTo}{in}\SetKwFor{For}{for}{\string:}{}%
    \SetKwIF{If}{ElseIf}{Else}{if}{:}{elif}{else:}{endif}%
    \SetKwFor{While}{while}{:}{endwhile}%
    \SetKwFor{For}{for}{:}{endfor}%
    \SetKw{or}{or}%
    \newcommand{\forcond}{$i$ \KwTo\Range{$n$}}%
    \AlgoDontDisplayBlockMarkers
    \SetKw{in}{in}%
    % additions (maybe you also need to uncomment the last two
    \SetProgSty{normalfont}%
    %\SetFuncArgSty{normalfont}%
    %\SetArgSty{normalfont}%
}

\newcommand{\basic}{%
    \DontPrintSemicolon
    \SetAlgoLined
    \SetKwInput{algoinput}{Eingabe}%
    \SetKwInput{algooutput}{Ausgabe}%
    \SetKw{return}{return}%
    \SetKw{and}{and}%
    \SetKw{continue}{continue}%
    \SetKw{in}{in}%
    \SetKw{to}{to}%
    \newcommand{\algotrue}{\return\texttt{True}}%
    \newcommand{\algofalse}{\return\texttt{False}}%
}

\newcommand{\eingabe}[1]{\algoinput{#1}}
\newcommand{\ausgabe}[1]{\algooutput{#1}}
\newcommand{\funktion}[2]{\Fn{#1}{#2}}

\begin{document}

\begin{algorithm}[H]
  \caption{This is an MWE} \label{algo: findjacobikandidat}

  \basic
  \pythonsyntax
  \eingabe{Some variables \texttt{a} and \texttt{b}}
  \ausgabe{Some other variables}
  \funktion{\texttt{wrongfont(h, k, p)}}{
    here is some command
  }
\end{algorithm}

\end{document}