shrink the line spacing with a `marginnote` environment

Question

I am struggling to shrink the line spacing with a marginnote environment. I can do it in a very minimal example, but not in my current full use case. Is it obvious to someone what I have in the full example that is overriding my definition of marginnote?

Minimal example that works as intended:

\documentclass[justified,twoside,symmetric]{tufte-book}
\usepackage{url}
\usepackage{hyperref}
\usepackage{mparhack} 
\usepackage{parskip}
\definecolor{ghr-blue}{cmyk}{0.846, 0.234, 0.00, 0.212}
\definecolor{ghr-orange}{cmyk}{0.0, 0.37, 0.757, 0.098}
\hypersetup{colorlinks,linkcolor=,urlcolor=ghr-orange}
\usepackage{fontawesome5}
\usepackage{lipsum}
\AtBeginEnvironment{marginnote}{\linespread{0.5}}
\begin{document}
\lipsum[1]
\marginnote{\faIcon{book-reader} Some text here more text here making long \href{https://tinyurl.com/af98yyak}{\footnotesize\texttt{tinyurl.com/af98yyak}}}
\lipsum[2]
\end{document}

Actual use case with unwanted extra space:

(some commands generated by {bookdown} R package I'm using to create tex file)

\documentclass[justified,twoside,symmetric,]{tufte-book}
% ams
\usepackage{amssymb,amsmath}
\usepackage{ifxetex,ifluatex}
\usepackage{fixltx2e} % provides \textsubscript
\ifnum 0\ifxetex 1\fi\ifluatex 1\fi=0 % if pdftex
  \usepackage[T1]{fontenc}
  \usepackage[utf8]{inputenc}
\else % if luatex or xelatex
  \makeatletter
  @ifpackageloaded{fontspec}{}{\usepackage{fontspec}}
  \makeatother
  \defaultfontfeatures{Ligatures=TeX,Scale=MatchLowercase}
  \makeatletter
  @ifpackageloaded{soul}{
     \renewcommand\allcapsspacing[1]{{\addfontfeature{LetterSpace=15}#1}}
     \renewcommand\smallcapsspacing[1]{{\addfontfeature{LetterSpace=10}#1}}
   }{}
  \makeatother
\fi
% graphix
\usepackage{graphicx}
\setkeys{Gin}{width=\linewidth,totalheight=\textheight,keepaspectratio}
% booktabs
\usepackage{booktabs}
% url
\usepackage{url}
% hyperref
\usepackage{hyperref}
% units.
\usepackage{units}
\setcounter{secnumdepth}{2}
% citations
\usepackage{natbib}
\bibliographystyle{apalike-etal}
% pandoc syntax highlighting
% longtable
\usepackage{longtable,booktabs}
% multiplecol
\usepackage{multicol}
% strikeout
\usepackage[normalem]{ulem}
% morefloats
\usepackage{morefloats}
% tightlist macro required by pandoc >= 1.14
\providecommand{\tightlist}{%
  \setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}
% title / author / date
\title{Global Health Research}
\author{Eric P. Green}
\date{2021-09-03}
\usepackage{booktabs}
\usepackage{mparhack} % https://tex.stackexchange.com/a/236380/30017
\usepackage{parskip}
% colors
\definecolor{ghr-blue}{cmyk}{0.846, 0.234, 0.00, 0.212}
\definecolor{ghr-orange}{cmyk}{0.0, 0.37, 0.757, 0.098}
\hypersetup{colorlinks,linkcolor=,urlcolor=ghr-orange}
% citations
\PassOptionsToPackage{round}{natbib}
\setcitestyle{super}
\renewcommand{\citep}[1]{{\cite{#1}}}
\renewcommand{\citet}[1]{{\cite{#1}}}
% icons
\usepackage{fontawesome5}
% break with tufte on subsubsections
\let\subsubsection\subsection
% fonts
\usepackage{fontspec}
\setmainfont{LibreBaskerville-Regular}
\setsansfont{SourceSansPro-Regular}
\setmonofont{Inconsolata}
\setsidenotefont{\fontspec{SourceSansPro-ExtraLight}[Scale=0.8]}
\setcaptionfont{\fontspec{SourceSansPro-ExtraLight}[Scale=0.8]}
\setmarginnotefont{\fontspec{SourceSansPro-ExtraLight}[Scale=0.8]}
\setcitationfont{\fontspec{SourceSansPro-ExtraLight}[Scale=0.8]\color{gray}}
% headers
\usepackage{fancyhdr}
\setlength{\headheight}{15pt}
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{ \markboth{#1}{} }
\renewcommand{\sectionmark}[1]{ \markright{#1} }
\fancyhf{}
\fancyhead[LE]{\thepage\space\space\space$\cdotp$\space\space\space\chaptername\space\thechapter}
\fancyhead[RO]{\leftmark\space\space\space$\cdotp$\space\space\space\thepage}
\fancypagestyle{plain}{ %
  \fancyhf{} % remove everything
  \renewcommand{\headrulewidth}{0pt} % remove lines as well
  \renewcommand{\footrulewidth}{0pt}
}
% title page and level headings
\usepackage[svgnames]{xcolor}
\usepackage{titlesec}
\usepackage{xhfill}
\colorlet{rulecolor}{Gainsboro!40!Lavender}
\usepackage{lipsum}
\titleformat{\chapter}[display]
{\filcenter}{\mbox{}\xrfill[0.4ex]{3pt}[rulecolor]\bfseries\sffamily{\large\enspace\chaptername\space\thechapter}\enspace\xrfill[0.4ex]{3pt}[rulecolor]\mbox{}}{0.3ex} {{\color{rulecolor}\titlerule[1pt]}\vskip3ex\huge\bfseries\sffamily}[\medskip{\color{rulecolor}\titlerule[1pt]}]
\usepackage{titling}
\pretitle{\begin{flushleft}\huge\bfseries}
\posttitle{\par\end{flushleft}}
\preauthor{\begin{flushleft}\Large\bfseries}
\postauthor{\par\end{flushleft}}
\predate{\begin{flushleft}\large\mdseries}
\postdate{\par\end{flushleft}}
\titleformat{\section}{\LARGE\bfseries\sffamily}
\titleformat{\subsection}{\Large\bfseries\sffamily}
\usepackage[svgnames]{xcolor}
% table of contents
\usepackage{titletoc}
\contentsmargin[1cm]{0cm}
\titlecontents{chapter}[0em]{\vskip12pt\Large\bfseries\sffamily}
{\thecontentslabel\enspace}
{\hspace{1.05em}}
{ \hfill\contentspage}[\vskip 6pt]
\titlecontents{section}[1em]{\mdseries\sffamily}
{\thecontentslabel\enspace}
{}
{\titlerule*[1pc]{.}\quad\contentspage}[\vskip 4pt]
\titlecontents{subsection}[2.7em]{\mdseries\sffamily}
{\thecontentslabel\enspace}
{}
{\titlerule*[1pc]{.}\quad\contentspage}[\vskip 3pt]
\usepackage{etoolbox}
\pretocmd{\contentsname}{\sffamily}{}{}
% margins
% The default minimum amount of space between \marginnotes is 10 pt.
\setlength\marginparpush{15pt}
\AtBeginEnvironment{marginfigure}{\linespread{0.5}}
\AtBeginEnvironment{marginnote}{\linespread{0.5}}
\makeatletter
\renewcommand{\footnotelayout}{@tufte@sidenote@font@tufte@sidenote@justification\linespread{0.5}}
\makeatother
% Remove \FloatBarrier from marginfigure definition
% to prevent unwanted spaces.
\makeatletter% so we can use @ commands
\renewenvironment{@tufte@margin@float}[2][-1.2ex]{%
  %\FloatBarrier% removed because it adds unwanted white space
  \begin{lrbox}{@tufte@margin@floatbox}%
  \begin{minipage}{\marginparwidth}%
    @tufte@caption@font
    \def@captype{#2}%
    \hbox{}\vspace*{#1}%
    @tufte@caption@justification
    @tufte@margin@par
    \noindent
}{%
  \end{minipage}%
  \end{lrbox}%
  \marginpar{\usebox{@tufte@margin@floatbox}}%
}
\makeatother% restore meaning of @
% quote
\usepackage[most]{tcolorbox}
\newtcolorbox{newquote}[1][]{%
    colback=black!5,
    colframe=black!5,
    notitle,
    sharp corners,
    borderline west={2pt}{0pt}{ghr-blue!80!black},
    enhanced,
    breakable,
    }
\renewcommand{\quote}{\newquote}
\renewcommand{\endquote}{\endnewquote}
% margin note
\usepackage{booktabs}
\usepackage{longtable}
\usepackage{array}
\usepackage{multirow}
\usepackage{wrapfig}
\usepackage{float}
\usepackage{colortbl}
\usepackage{pdflscape}
\usepackage{tabu}
\usepackage{threeparttable}
\usepackage{threeparttablex}
\usepackage[normalem]{ulem}
\usepackage{makecell}
\usepackage{xcolor}
\begin{document}
\lipsum[1]
\marginnote{\faIcon{book-reader} Some text here more text here making long \href{https://tinyurl.com/af98yyak}{\footnotesize\texttt{tinyurl.com/af98yyak}}}
\lipsum[2]
\end{document}

Answer 1

Use

\begin{marginfigure}
\faIcon{book-reader} Some text here more text here making long Some text here more text here making long Some text here more text here making long \href{https://tinyurl.com/af98yyak}{\footnotesize\texttt{tinyurl.com/af98yyak}}
\end{marginfigure}

Or add to your preamble

\makeatletter
\renewcommand\marginnote[2][0pt]{%
    \ifthenelse{\boolean{@tufte@loadnatbib}}{%
        \let\cite\@tufte@infootnote@cite%   use the in-sidenote \cite command
    }{}%
    \gdef\@tufte@citations{}%           clear out any old citations
    \marginpar{\hbox{}\vspace*{#1}\setstretch{0.5}\@tufte@marginnote@font\@tufte@marginnote@justification\@tufte@margin@par\vspace*{-1\baselineskip}\noindent #2}%
    \@tufte@print@citations%            print any citations
    \ifthenelse{\boolean{@tufte@loadnatbib}}{%
        \let\cite\@tufte@normal@cite%       go back to using normal in-text \cite command
    }{}%
}
\makeatother

to use \marginnote{...}