Translatable developer and application names
It seems I was wrong about untranslatable developer and application names.
If you think these areas should be translatable you can remove translatable=no tags.
Sorry for my mistake.
<developer_name translatable="no">Florian Müllner</developer_name>
<developer id="fmuellner@gnome.org">
<name translatable="no">Florian Müllner</name>
</developer>
Also
Appstream decided to use reverse DNS for developer IDs.
The element should have a id property, containing a unique ID to identify the component developer / development team. It is recommended to use a reverse-DNS name, like org.gnome or io.github.ximion, or a Fediverse handle (like @user@example.org) as ID to achieve a higher chance of uniqueness.
More information: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-developer