Federation of contacts / addressbook between murena.io and another Nextcloud instance


I would like to use my /e/OS phone contacts, which are synced to my murena.io cloud (which is a Nextcloud under the hood), in another Nextcloud of mine.

Nextcloud offers federation between servers for this. To make addressbook federation work, you need to make the Nextcloud servers known to each other as TrustedServers.
After configuring murena cloud as TrustedServer in the admin/sharing section of my Nextcloud instance, it shows yellow. To make it green, apparently my Nextcloud instance also needs to be known to murena as TrustedServer as well. But in the config of my murena account I do not have access to this section.

What can I do to make my Nextcloud instance known to murena cloud as TrustedServer?

Or is there any other way to make addressbook federation work between a Nextcloud instance and murena cloud?

Thanks for your thoughts!

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