Collabora

Collabora Online is an application from the default repository. Documentation can be found here

install nextcloud in ns8, then install Nextcloud Office (richdocuments) by the web interface of the administrator session (alternatively a bulk of default software is proposed at the first admin login creation, just accept it) then go to Settings > Administration > Office and set the correct url to collabora (verify the certificate or not in case of self-signed)

or ssh to nextcloud and install it by hand

ssh nextcloud1@localhost

.config/bin/occ  app:install richdocuments
.config/bin/occ config:app:set richdocuments wopi_url --value=https://collabora.domain.com
.config/bin/occ app:enable richdocuments

then exit

exit