I searched this community and couldn’t find anything about odt, I found a few odt viewers on F-Droid and Aurora when I searched ‘odt’, but the only editors for odt, were ironically the proprietary Google Documents and Microsoft Word.
Have you found anything else?
May I ask why? Using alternative sources from the vendors themselves usually isn’t any less secure than using the official F-Droid repos. It’s a common thing on Linux.
Has Collabora made its packages reproducible, so independent people can check if their package is built from the source code without modification?