I think you did a good job. Plus there are so many permutations of server out there and they all have their issues. I am using OpenMediaVault which is seems has some of its own quirks.
I'm having a few issues that maybe you can clue me in on. I'm new to the world of port forwarding and I have a weird double router situation going on but I am having some strange issues with my local IP when I try and access nextcloud.
All I am trying to really do is access it locally, without having to use my DuckDNS, and that seems to be failing for some reason after running these container scripts. I am sure this is user error.
I figured I'd go to https://LOCALIP:457 and see my NextCloud admin backend. I just see a "welcome to your swag instance" page. I believe that also happens when I go to https://DUCKDNSADDRESS:457. I can't seem to find ANY way to get back to the nextcloud admin backend (only the standard settings screen you see as an admin USER if that makes sense).