Installing on NextCloud

I posted the following problem on the NextCoud forum a few days ago, but so far had no response - so I thought that I’d try here:

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

Are you trying to install this app in Nextcloud: Collabora Online - Built-in CODE Server (ARM64) ?

Yes - I am.

Thanks for the reply.