I have a warning about WOPI: You have not configured the allow-list for WOPI requests. Without this setting users may download restricted files via WOPI requests to the Nextcloud server. Click here for more info
Are you running that cURL test from inside of the Nextcloud container?
Essentially, make sure that your Nextcloud container is not bypassing the reverse proxy to reach the Collabora container.
Depending on what instructions you followed, it is possible for the Collabora container to have HTTPS enabled on it as well, but it would not be using the LE certs deployed on your reverse proxy.
Edit: To test my theory: IIRC thereās also an app setting called disable_certificate_verification or the like (in the richdocuments app in NC). I believe something for it appears in the web UI in the settings area when youāve set NC Office to use your own server (rather than the built in one) so you donāt need even need to do it from the CLI.
This will turn off certificate validation at the NC server level for the capabilities check. If things work you can then decide whether youāre comfortable with the two internal containers talking to each other without verification of certificates or not. If so, youāre done. If not, youāll have to make adjustment to your environment so that NC is not bypassing the proxy.
I had a similar issue, running Nextcloud on an Ubuntu server with Apache, reverse proxy, and an SSL certificate for Collabora on a Docker image. The trick for me was to add port 443.
Of course, you have to replace the nextcloud domain name with yours.
sudo docker run -t -d -p 127.0.0.1:9980:9980 -e 'domain=nextcloud\\.com:443' -e 'dictionaries=de en es sv ..' -e 'TZ=Europe/Stockholm' --restart always --cap-add MKNOD --privileged collabora/code