Installation of Collabra Online

I’m running NextCloud 20.0.2.2 in a Docker image on a Raspberry Pi 4.

I’d like to install the Collabra Online app, but can’t install the server. I get the error:

This app cannot be installed because the following dependencies are not fulfilled:
The following architectures are supported: aarch64 

I’d be gratefull for any help, please.
Jim