I solved it by myself: Install collabora online docker with additional dictionaries (languages) Tutorial
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Is there an easy way to install more dictionaries with the default docker image?
Currently there are much less installed than possible, which is sad if you speak an other language.
Is building an own image with https://github.com/CollaboraOnline/Docker-CODE the only way, or is there a easier way?
Building an own image, updating it is for me far harder then the “normal” docker installation.