[tex-live] TL2018: Problems with filenames

[David Carlisle]

I really have no idea, but chatting with ulrike (who has the windows
build) suggests that

pdflatex \input\detokenize{Begrüßung}

should work, which may at least give you a workaround.

there were some changes for latex here but they should affect all
non-ascii letters the same way, and the fact that xetex fails
shouldn't be related but seems to imply something odd about the
encoding of that filename.