Beamer highlight current item in list both in bold and with another item symbol

Question

1. Suppose that I have an itemize list, which I want to present in sequential order. I use [<+->] for that.
2. I want to highlight the current (the most recently added) item in bold. To do so, I replace [<+->] with [<+-|alert@+>] and change alert color and font following this answer:

\setbeamercolor{alerted text}{fg=black} %change the font color
\setbeamerfont{alerted text}{series=\bfseries} %make alerted text bold

Result with current item in bold:

3. Moreover, I want to change the item shape from a circle to a triangle only for the most recently added item to the list. Following this answer, I modify alert behaviour in itemize:

\AtBeginEnvironment{itemize}{%
\renewenvironment{alertenv}{\only{\setbeamertemplate{items}[triangle]}}{}}

However, since I've redefined alert environment, the bold for current item is no longer working:

4. This is the result I want to achieve (combination of two modifications at the same time):

MWE:

\documentclass{beamer} 
\usetheme{metropolis}
\begin{document}
% redefining alert action only for itemize
\AtBeginEnvironment{itemize}{%
\renewenvironment{alertenv}{\only{\setbeamertemplate{items}[triangle]}}{}}
\begin{frame}{Future work}
\begin{itemize}[<+-|alert@+>]
    \setbeamercolor{alerted text}{fg=black} %change the font color
    \setbeamerfont{alerted text}{series=\bfseries} %make alerted text bold
    \item Fix the global warming
    \item Prove P $\ne$ NP
    \item Sofa in the office 
\end{itemize}
\end{frame}
\end{document}

Answer 1

You could use the \alt macro to provide an alternative symbol:

\documentclass{beamer} 
\usetheme{moloch}% modern fork of the metropolis theme
\setbeamertemplate{itemize item}{\usebeamerfont*{itemize item}\alt<.>{\raise1.25pt\hbox{\donotcoloroutermaths$\blacktriangleright$}}{\textbullet}}
\begin{document}
\begin{frame}{Future work}
\begin{itemize}[<+-|alert@+>]
    \setbeamercolor{alerted text}{fg=black} %change the font color
    \setbeamerfont{alerted text}{series=\bfseries} %make alerted text bold
    \item Fix the global warming
    \item Prove P $\ne$ NP
    \item Sofa in the office 
\end{itemize}
\end{frame}
\end{document}