Typesetting special characters from European and Asian languages with the fewest potential side effects

I am using the libertine and libertinust1math packages, in conjunction with the book document class.

The preamble to my thesis is long (> 1400 lines) and includes dozens of packages in addition to the libertine and libertinust1math packages mentioned above.

I have a large number of bibliographic entries in my thesis, and I need to use several characters from European and Asian languages. What is the best way in which to obtain these characters, with the lowest probability of side effects resulting from the dozens of packages used in my thesis?

The following MWE, which contains only a small fraction of the packages I am using in my thesis, gives a list of the characters that I need. Most of them I have already found in kernel commands. However, a few — marked below with arrows — I am still looking for.

For those characters — "D with stroke," "e with tail," "L with slash," and "l with slash" — it appears that there are multiple ways of obtaining them. What method(s) are likely to have the fewest potential side effects?

documentclass[oneside,11pt]{book}

usepackage[semibold,tt=false]{libertine}
usepackage{libertinust1math}
usepackage[
  expansion = false ,
  tracking = smallcaps ,
  letterspace = 40 ,
  final
]{microtype}
usepackage[font={sf,small},labelsep=quad,labelfont=sc]{caption}
usepackage[subrefformat=parens]{subcaption}
usepackage{mathtools}
usepackage{booktabs}
usepackage{etoolbox}
usepackage{siunitx}
sisetup{%
  detect-family, detect-shape, detect-weight,
  product-units = power,
  list-final-separator = {, and },
  retain-explicit-plus,
  input-comparators = {<=>approxgegeqggleleqllsimlesssimgtrsim}
}

begin{document}

begin{table}[!h]
  centering
  begin{tabular}{rlcll}
    toprule
    & ~{a} & verb|~{a}| & ``a with tilde on top'' & Portuguese, Vietnamese, ...
    & '{c} & verb|'{c}| & ``c with acute accent'' & Polish, Croatian, ...
    & c{c} & verb|c{c}| & ``c with cedilla'' & French, Catalan, Portuguese, Turkish, Turkmen, ...
    & v{c} & verb|v{c}| & ``c with v on top'' & Czech, Croatian, Slovak, Slovene, Latvian, ...
    $rightarrow$ & D & ? & ``D with stroke'' & Serbo-Croatian, Vietnamese, ...
    $rightarrow$ & e & ? & ``e with tail'' & Polish, Lithuanian, ...
    $rightarrow$ & L & ? & ``L with slash'' & Polish, ...
    $rightarrow$ & l & ? & ``l with slash'' & Polish, ...
    & ^{o} & verb|^{o}| & ``o with circumflex'' & French, ...
    & o & verb|o| & ``o with slash'' & Danish, Norwegian, Faroese, ...
    & v{R} & verb|v{R}| & ``R with v on top'' & Czech, ...
    & v{s} & verb|v{s}| & ``s with v on top'' & Czech, ...
    & H{u} & verb|H{u}| & ``u with double acute accent'' & Hungarian, ...
    & "{u} & verb|"{u}| & ``u with umlaut'' & German, Hungarian, Turkish, Turkmen, ...
    & '{y} & verb|'{y}| & ``y with acute accent'' & Czech, Slovak, Turkmen, Icelandic, ...
    bottomrule
  end{tabular}
end{table}

end{document}