Umlaut in the name of the file containing the preamble

Question

Using \input{filename} for a file in a subdir works fine even including the whole preamble, but when the targeted file has an Umlaut in its name, I get an Emergency stop with a Missing \begin{document}. Including the file after having hardlinked it (I only changed the Umlaute in the name) works fine. But that's not what I intended.

I'd like to include the preamble being in another file into my actual *.tex file where the name of the included file contains Umlaute.

I'm not sure wether I stay with my actual \documentclass{report}. Does the behaviour of \input or \include depend on the used documentclass?

Executed command: $ latexmk -pdf -synctex=1 mwe-main.tex
mwe-main.tex (trying to keep the example files minimal)

\input{../ümwe}
\lipsum
\end{document}

ümwe.tex (in the parent dir)

\documentclass[a4paper,12pt,ngerman]{report}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lipsum}
\begin{document}
    \newcommand{\n}{\newline}

mwe-main.log

This is pdfTeX, Version 3.14159265-2.6-1.40.19 (TeX Live 2019/dev/Debian) (preloaded format=pdflatex 2020.12.3)  29 SEP 2022 19:23
entering extended mode
 restricted \write18 enabled.
 %&-line parsing enabled.
**mwe-main.tex
(./mwe-main.tex
LaTeX2e <2018-12-01>
! LaTeX Error: Missing \begin{document}.
See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...
l.1 \input{../ümwe}
? H
You're in trouble here.  Try typing  <return>  to proceed.
If that doesn't work, type  X <return>  to quit.
? H
Sorry, I already gave what help I could...
Maybe you should try asking a human?
An error might have occurred before I noticed any problems.
``If all else fails, read the instructions.''
? H
Sorry, I already gave what help I could...
Maybe you should try asking a human?
An error might have occurred before I noticed any problems.
``If all else fails, read the instructions.''
? 
LaTeX Font Info:    Try loading font information for +cmr on input line 1.
LaTeX Font Info:    No file cmr.fd. on input line 1.
LaTeX Font Warning: Font shape /cmr/m/n' undefined (Font) using/cmr/m/n' instead on input line 1.
! Corrupted NFSS tables.
wrong@fontshape ...message {Corrupted NFSS tables}
                                                  error@fontshape else let f...
l.1 \input{../ümwe}
? H
This error message was generated by an \errmessage
command, so I can't give any explicit help.
Pretend that you're Hercule Poirot: Examine all clues,
and deduce the truth by order and method.
?
LaTeX Font Warning: Font shape /cmr/m/n' undefined (Font) usingOT1/cmr/m/n' instead on input line 1.
Missing character: There is no m in font nullfont!
Missing character: There is no w in font nullfont!
Missing character: There is no e in font nullfont!
! Undefined control sequence.
\UseTextAccent ...up @firstofone \let @curr@enc 
                                                  \cf@encoding @use@text@en...
l.1 \input{../ümwe}
? H
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), typeI' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
? 
! Undefined control sequence.
\GenericError  ...

                                                    #4  \errhelp @err@     ...
l.1 \input{../ümwe}
? H
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), typeI' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
? H
Sorry, I already gave what help I could...
Maybe you should try asking a human?
An error might have occurred before I noticed any problems.
``If all else fails, read the instructions.''
? 
! Undefined control sequence.
\GenericError  ...

                                                  \let @err@               ...
l.1 \input{../ümwe}
? H
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), typeI' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
? H
Sorry, I already gave what help I could...
Maybe you should try asking a human?
An error might have occurred before I noticed any problems.
``If all else fails, read the instructions.''
? 
! Undefined control sequence.
\GenericError  ...

                                                  @empty \def \MessageBreak...
l.1 \input{../ümwe}
? 
! Undefined control sequence.
\GenericError  ...

                                                     \endgroup 
l.1 \input{../ümwe}
? 
! Undefined control sequence.
\GenericError  ...

                                                    #4  \errhelp @err@     ...
l.1 \input{../ümwe}
? H
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), typeI' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
? H
Sorry, I already gave what help I could...
Maybe you should try asking a human?
An error might have occurred before I noticed any problems.
``If all else fails, read the instructions.''
? X
Here is how much of TeX's memory you used:
 19 strings out of 494435
 263 string characters out of 6173463
 52519 words of memory out of 5000000
 3802 multiletter control sequences out of 15000+600000
 3640 words of font info for 14 fonts, out of 8000000 for 9000
 59 hyphenation exceptions out of 8191
 18i,1n,19p,58b,88s stack positions out of 5000i,500n,10000p,200000b,80000s
No pages of output.
PDF statistics:
 0 PDF objects out of 1000 (max. 8388607)
 0 named destinations out of 1000 (max. 500000)
 1 words of extra memory for PDF output out of 10000 (max. 10000000)