M-x elfeed RET shows the following

Why are umlauts not properly rendered?
C-u C-x = on a properly rendered character shows:

C-u C-x = on a wrongly rendered character shows (e.g. \303) shows:

Only elfeed is unable to display the umlauts properly. Gnus, eww, circe, and other emacs packages show the umlauts properly on my system.
I'm using
GNU Emacs 29.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.34, cairo version 1.16.0) of 2023-04-06
and
elfeed-version is 3.4.1