OnlyOffice appears to have removed their Android app from their repos: https://github.com/ONLYOFFICE/documents-app-android
It can still be found on an archive: https://archive.softwareheritage.org/browse/origin/directory/?origin_url=https%3A%2F%2Fgithub.com%2FONLYOFFICE%2Fdocuments-app-android
This means if you are de-Googled like me, they are no longer an option.
Perhaps coincidentally, they have also started making legal claims against the EuroOffice fork: https://github.com/ONLYOFFICE#️-legal-note
I will take a look at this one. Does it require the server side to be running? I’m not a fan of server side because it’s a streaming session vs HTML-based.
Collabora does not, it is only on device, based on Libre Office. I save LibreOffice files in Tresorit for cloud sync because Proton Drive does not have a Linux client. Collabora allows you to open and edit files from Tresorit and resave it there instead of downloading, editing, and reuploading. Ideally I make the original file on Linux since my default save location can be Tresorit, and edit on Android, but I can always upload a template to Tresorit manually on Android, and then reopen to edit and save in Tresorit.
Proton Docs is cloud only.