Scratch number 3 above. While you can connect to the Collabora container on the admin panel, it fails to open documents without the nginx server.
(continuing from above)
- Because I was operating on a local network, the DNS for nextcloud.example.com and nextcloud.example.com were not working well. I resolved the problem by adding the following onto the nginx and collabora containers.
extra_hosts:
- "nextcloud.example.com:192.168.1.21"
- "collabora.example.com:192.168.1.21"