Collabora from snap install does not work via HTTPS

I installed NC21 on Ubuntu 20.04 using snap.
I enabled HTTPS via lets-encrypt and added the used domain to “trused_domains”.
When I access Nextcloud via HTTP I can open documents using Collabora, but when I use HTTPS Collabora fails to load. I see no obvious errors in the logs on the server ( /var/snap/nextcloud/28403/logs) or in the browser console. Is this not supposed to work because the collabora executable running as a backend unable to handle the SSL stuff?
Do I have to handle the certificate stuff separately for collabora? How would i do that?