I want to preface this post by apologizing in advance if this is a problem with a glaringly obvious solution and by freely admitting that I'm very new to this sort of thing, am learning as I go, and have found this forum to be a magnificent resource so far (thanks!)
With the help of a couple of KM0201's instructive how-to guides, I was able to get up and running with Nextcloud running with Swag, Collabora, and DuckDNS fairly easily. At the moment, I've got Nextcloud Office up and running with my self-hosted Collabora/Code server. It all seems fully usable. But I'm getting a warning message about not having configured my WOPI allow-list. I've searched online high and low for what to put in there, and none of what I'm finding is working. If I understand correctly, the purpose of this allow-list is to prevent unwanted access to my files from unknown IP addresses. I need to be able to access and use Nextcloud Office from outside my local network, but I have a VPN configured so I think I really only need to allow local IP addresses. No matter what I put into the text-input box, though, once I hit enter, the text in the box just disappears and the warning persists.
From my Google-ing, I know this is supposed to be a comma-seperated list with no spaces, and I've tried suggestions I've found including my public IP, my router/firewall's gateway address, 127.0.0.1, the IP of my Collabora docker container, and combinations thereof, without any luck.
Any suggestions / troubleshooting help would be very appreciated!