Edit: OnlyOffice does not support it’s own Nextcloud integration via mobile apps at this time. Wow, this is very unfortunate news. Click here to see the open Github issue.
You can request mobile app support by kindly emailing OnlyOffice directly at email@example.com
No longer relevant, but I’ll leave here any case anyone runs into this issue…
I see the option to login into personal or portal accounts via the official OnlyOffice Android App. I’ve tried logging in with both options unsuccessfully. Also tried using my main password vs. one-time passwords with no success.
Asks for my.server.com domain, user name and password. Perhaps personal Nextcloud instances are not supported at all… I see users can use OnlyOffice’s own cloudstorage, Facebook, or Google credentials to create a supported account.