Created attachment 147546 [details]
Error when in French (left) and no error when in English (right)

SUMMARY
Whenever trying to download themes or colour schemes or window decorations from systemsettings with systemsettings running in another language than English, the window returns an error "Unknown Open Collaboration Service API error. (0)" (here I translated the error message). However, when running systemsettings in English, there is no bug.

STEPS TO REPRODUCE
1. Use KDE in e.g. French (for instance in a fresh installed VM)
2. Open systemsettings (Discover)
3. Try to download a theme or window decoration within the Appearance menu. This does not work.
4. Then open a terminal and run `LANG=C systemsettings` where LANG=C stands for default US English.
5. Try again, and now it works (but it is in English, which may not be the user's language).

SOFTWARE/OS VERSIONS
Linux kernel: 5.13.0-35-generic
Distro: Kubuntu with enabled KDE backports
KDE Plasma Version: 5.24.3
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
I tagged the 15-Minutes Bug Initiative in the title because changing themes is what many people do in the first 15 minutes AND the bug is reproducible on a freshly installed KDE Neon VM set-up to French during the install, which I tried out. There is also someone pointing to this on an Arch forum: https://bbs.archlinux.org/viewtopic.php?id=257236

IMPORTANT
Note that I am not sure it has to do with systemsettings directly, because whenever a theme or colour scheme or kwin script is installed and gets an update in plasma-discover, plasma-discover would fail at doing the update unless I run it in English (`LANG=C plasma-discover`).