Please run

zypper locales
rpm -q --provides dolphin-part dolphin-part-lang

(In reply to Fabian Vogt from comment #1)
> Please run
> 
> zypper locales

Code  | Language              | Requested
------+-----------------------+------------
de    | Deutsch               | Fallback
de_DE | Deutsch (Deutschland) | Angefordert
en    | Englisch              | Fallback

> rpm -q --provides dolphin-part dolphin-part-lang

dolphin-part = 23.08.5-bp156.1.1
dolphin-part(x86-64) = 23.08.5-bp156.1.1
libdolphinprivate.so.5()(64bit)
dolphin-lang = 23.08.5
dolphin-part-lang = 23.08.5-bp156.1.1
dolphin-part-lang-all = 23.08.5

Created attachment 874261 [details]
yast installer

This is a screenshot from the Yast installer, showing that dolphin-part-lang is not selected. 
After installation, Dolphin will be in English, ignoring the selected language, and dolphin-part-lang needs to be additionally installed.
You can check this yourself in a virtual machine before installing the distribution by going to Installation Setting -> Software -> Details

dolphin-part is missing all locale(dolphin-part:lang) provides, which indicates that support for those is missing in RPM. Many packages touched recently rely on that, so it's probably more than just dolphin-part being affected.

Workaround for dolphin submitted: sr 1167565

Maybe we should backport the locale provides from RPM into kf5-filesystem, but that's a SLE package and it's past the submission deadline and it can't easily be fixed in a maintenance update.

This is an autogenerated message for OBS integration:
This bug (1222694) was mentioned in
https://build.opensuse.org/request/show/1167565 Backports:SLE-15-SP6 / dolphin