Here an attempt to recreate the look of your theme without the metropolis theme:
beamerthememetropolix.sty:
```
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Colours
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\definecolor{mDarkBrown}{HTML}{604c38}
\definecolor{mDarkTeal}{HTML}{23373b}
\definecolor{mLightBrown}{HTML}{EB811B}
\definecolor{mLightGreen}{HTML}{14B03D}
\setbeamercolor{normal text}{fg=black!2,bg=mDarkTeal}
\usebeamercolor[fg]{normal text}
\setbeamercolor{alerted text}{fg=mLightBrown}
\setbeamercolor{example text}{fg=mLightGreen}
\setbeamercolor{titlelike}{use=normal text, parent=normal text}
\setbeamercolor{author}{use=normal text, parent=normal text}
\setbeamercolor{date}{use=normal text, parent=normal text}
\setbeamercolor{institute}{use=normal text, parent=normal text}
\setbeamercolor{structure}{use=normal text, fg=normal text.fg}
\setbeamercolor{palette primary}{use=normal text,fg=normal text.bg, bg=normal text.fg}
\setbeamercolor{frametitle}{use=palette primary,parent=palette primary}
\setbeamercolor{block body alerted}{use=block body, parent=block body}
\setbeamercolor{block body example}{use=block body, parent=block body}
\setbeamercolor{footnote}{fg=normal text.fg!90}
\setbeamercolor{footnote mark}{fg=.}
\setbeamercolor{author in head/foot}{fg=.,bg=}
\setbeamercolor{section in head/foot}{bg=normal text.bg, fg=structure.fg}
\setbeamercolor{subsection in head/foot}{bg=normal text.bg, fg=structure.fg}
\setbeamercolor{title in head/foot}{fg=normal text.fg}
\setbeamercolor{page number in head/foot}{fg=normal text.fg}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Fonts
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\setbeamerfont{title}{size=\Large,series=\bfseries}
\setbeamerfont{author}{size=\small}
\setbeamerfont{date}{size=\small}
\setbeamerfont{section}{size=\Large,series=\bfseries}
\setbeamerfont{block title}{size=\normalsize,series=\bfseries}
\setbeamerfont{block title alerted}{size=\normalsize,series=\bfseries}
\setbeamerfont{subtitle}{size=\large,series=\normalfont}
\setbeamerfont{frametitle}{size=\large,series=\bfseries}
\setbeamerfont{caption}{size=\small}
\setbeamerfont{caption name}{series=\bfseries}
\setbeamerfont{description item}{series=\bfseries}
\setbeamerfont{page number in head/foot}{size=\scriptsize}
\setbeamerfont{author in head/foot}{size=\scriptsize}
\setbeamerfont{title in head/foot}{size=\scriptsize}
\setbeamerfont{bibliography entry author}{size=\normalsize,series=\normalfont}
\setbeamerfont{bibliography entry title}{size=\normalsize,series=\bfseries}
\setbeamerfont{bibliography entry location}{size=\normalsize,series=\normalfont}
\setbeamerfont{bibliography entry note}{size=\small,series=\normalfont}
\setbeamerfont{section in head/foot}{series=\bfseries,size=\scriptsize}
\setbeamerfont{section in head/foot shaded}{series=\normalfont,size=\scriptsize}
\setbeamerfont{subsection in head/foot}{series=\bfseries,size=\scriptsize}
\setbeamerfont{subsection in head/foot shaded}{series=\normalfont,size=\scriptsize}
\setbeamerfont{title in head/foot}{size=\scriptsize}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Misc settings
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% defining a custom headline
\setbeamertemplate{headline}{%
\begin{beamercolorbox}[ht=10ex,dp=0ex]{section in head/foot}
\insertsectionnavigationhorizontal{\paperwidth}{}{}\strut\par
\insertsubsectionnavigationhorizontal{\paperwidth}{}{\hskip0pt plus1filll}\strut
\end{beamercolorbox}%
}
% like the default frametitle, but taller
\setbeamertemplate{frametitle}{%
\ifbeamercolorempty[bg]{frametitle}{}{\nointerlineskip}%
\@tempdima=\textwidth%
\advance\@tempdima by\beamer@leftmargin%
\advance\@tempdima by\beamer@rightmargin%
\begin{beamercolorbox}[sep=0.3cm,left,wd=\the\@tempdima]{frametitle}
\usebeamerfont{frametitle}%
\vbox{}\vskip0ex% <- change frametitle height here
\if@tempswa\else\csname beamer@fteleft\endcsname\fi%
\strut\insertframetitle\strut\par%
{%
\ifx\insertframesubtitle\@empty%
\else%
{\usebeamerfont{framesubtitle}\usebeamercolor[fg]{framesubtitle}\strut\insertframesubtitle\strut\par}%
\fi
}%
\vskip0ex% <- change frametitle height here
\if@tempswa\else\vskip-.3cm\fi% set inside beamercolorbox... evil here...
\end{beamercolorbox}%
}
% replicate title page
\setbeamertemplate{title page}{
\vbox{}
\vfill
\begingroup
{\usebeamercolor[fg]{titlegraphic}\inserttitlegraphic\par}
\centering
\begin{beamercolorbox}[sep=8pt,center,left]{title}
\usebeamerfont{title}\inserttitle\par%
\ifx\insertsubtitle\@empty%
\else%
\vskip0.25em%
{\usebeamerfont{subtitle}\usebeamercolor[fg]{subtitle}\insertsubtitle\par}%
\fi%
\end{beamercolorbox}%
\vskip0.7em\par
\begin{beamercolorbox}[sep=8pt,center,left]{title}
\textcolor{mLightBrown}{\rule{\dimexpr\linewidth-16pt}{0.5pt}}
\end{beamercolorbox}
\vskip0.7em\par
\begin{beamercolorbox}[sep=8pt,center,left]{author}
\usebeamerfont{author}\insertauthor
\end{beamercolorbox}
\vskip-0.8em
\begin{beamercolorbox}[sep=8pt,center,left]{date}
\usebeamerfont{date}\insertdate
\end{beamercolorbox}
\vskip-0.5em
\begin{beamercolorbox}[sep=8pt,center,left]{institute}
\usebeamerfont{institute}\insertinstitute
\end{beamercolorbox}
\vskip0.5em
\endgroup
\vfill
}
% replicating the section page
\setbeamertemplate{section page}{
\begin{frame}[plain,c]
\centering
\begin{minipage}{.7\textwidth}
\begin{beamercolorbox}[sep=8pt,left]{section}
\usebeamerfont{section}\insertsectionhead
\end{beamercolorbox}
\begin{beamercolorbox}[sep=8pt,left]{title}
\textcolor{mLightBrown}{\rule{\dimexpr\linewidth-16pt}{0.5pt}}
\end{beamercolorbox}
\end{minipage}
\end{frame}
}
\AtBeginSection{\usebeamertemplate{section page}}
% custom footline
\setbeamertemplate{footline}{%
\leavevmode%
\hbox{%
\begin{beamercolorbox}[wd=\paperwidth,ht=2.25ex,dp=1ex,leftskip=2ex,rightskip=2ex]{author in head/foot}%
\usebeamerfont{author in head/foot}\insertshortauthor\expandafter\ifblank\expandafter{\beamer@shortinstitute}{}{~|~\insertshortinstitute}
\hfill
\usebeamerfont{title in head/foot}\insertshorttitle
\hfill%
\usebeamercolor[fg]{page number in head/foot}%
\usebeamerfont{page number in head/foot}%
\usebeamertemplate{page number in head/foot}%
\end{beamercolorbox}}%
\vskip0pt%
}
\setbeamertemplate{page number in head/foot}[totalframenumber]
% switch off navigation symbols
\setbeamertemplate{navigation symbols}{}
% loading metropolis pgfplots set
\usepackage{pgfplots}
\usepackage{pgfplotsthemetol}
```
A short test document:
```
\documentclass[
aspectratio = 1610,
onlytextwidth,
t
]{beamer}
\usepackage[T1]{fontenc}
\usepackage{noto}
\usetheme{metropolix}
\title{title title title title}
\subtitle{subtitle subtitle subtitle subtitle subtitle}
\date{\today}
\author{author author}
\institute{institute institute}
\begin{document}
\begin{frame}[plain,c]
\titlepage
\end{frame}
\begin{frame}[plain]{Overview}
\tableofcontents[hideallsubsections]
\end{frame}
% ### SECTION
% --- --- ---
\section{section1}
% ## SUB-SECTION
% --- ---
\subsection{subsection1.1}
\begin{frame}
\frametitle{frametitle}
\end{frame}
% ## SUB-SECTION
% --- ---
\subsection{subsection1.2}
\begin{frame}
\frametitle{frametitle}
\end{frame}
% ### SECTION
% --- --- ---
\section{section2}
% ## SUB-SECTION
% --- ---
\subsection{subsection2.1}
\begin{frame}
\frametitle{frametitle}
\end{frame}
% ## SUB-SECTION
% --- ---
\subsection{subsection2.2}
\begin{frame}
\frametitle{frametitle}
\end{frame}
% ### SECTION
% --- --- ---
\section{section3}
% ## SUB-SECTION
% --- ---
\subsection{subsection3.1}
\begin{frame}
\frametitle{frametitle}
\end{frame}
% ## SUB-SECTION
% --- ---
\subsection{subsection3.2}
\begin{frame}
\frametitle{frametitle}
\end{frame}
\end{document}
```
