on topic of duplicate claims - I tested Tell Latex to ignore ALL unicode errors? - "solution" it resulted in LaTeX displaying "?" rather than "⌀".
Thanks to people who provided high quality and very useful answers.
I added ⌀ to text and now pdflatex is crashing with
Package inputenc Error: Unicode char \u8:⌀ not set up for use with LaTeX.
I know that I can use \DeclareUnicodeCharacter or similar to introduce special handling of this character but doing it every time that new UTF-8 character appears in the input is not acceptable.
It needs to work in pdflatex (or other pdf-generating latex compiler) as I use latex solely as pdf generator (LaTeX is generated from input, pdflatex generates pdf output).
MWE:
\begin{document}
⌀
\end{document}
MWE with my document declarations present
\documentclass{article}
\usepackage[a4paper, total={6.5in, 10.5in}]{geometry}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{cprotect}
\usepackage{fvextra}
\usepackage{textcomp}
% make TOC work correctly
\makeatletter
\def\l@section{\@dottedtocline{1}{1em}{2em}}
\makeatother
\usepackage{index}
\makeindex
\DeclareUnicodeCharacter{00A0}{~}
\DefineVerbatimEnvironment{escape}
{Verbatim}
{fontfamily=\rmdefault,breaklines,breaksymbolleft={}}
\CustomVerbatimCommand\escapeinline{Verb}{fontfamily=\rmdefault,breaklines,breaksymbolleft={}}
\begin{document}
⌀
\end{document}
inputenc
mostly just supports alphabetic characters and punctuation. If you want to use technical characters (like the diameter symbol ⌀) it's better to use an engine with native UTF-8 support.\documentclass{article}\usepackage{fontspec}\begin{document}⌀\end{document}