https://blog.documentfoundation.org/blog/2025/08/15/guide-to-migrating-from-proprietary-formats-to-odf/
Really nice blog from the Documentfoundation on how to migrate Microsoft Office Document formats to open document format. Maby someone can make use of this, when not yet migrated to a free document writer suite.
I personally just found out, that Libre Office also offers an easy to use GPG-signing process for odf-documents.