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?
Collabora Office is the label on my Icon. Same as the name in Play. The Play publisher is Collabora Productivity limited. Rating 4.2 and user count 500K or more.
I do not actually use it much but a family member uses it all the time on their tablet. For me I use mostly Joplin for notes on Android.