Need to upgrade data version by downgrading nextcloud docker image version

Okay, let me start by saying I'm at my wits end with this. Nextcloud has literally never worked. This is an extra project for me so I've had this on the bac-burner for a while, probably over a year and I've spent about 8 hours trying to figure things out. 

Put simply, I've never been able to access the web ui since installing nextcloud (linus server repository)...a while ago. Clicking the "webui" button in unraid or going directly to the ip address itself, I get a "site cannot be reached" ERR_CONNECTION_REFUSED.  

I wanted nextcloud to be a replacement for google drive so I wanted to set it up with a custom domain and things so I'm using cloudflare, Nginx Proxy Manager, port forwarding on my router and all that jazz. I can access jellyfin and 2 other docker apps through the domain name but never nextcloud, even though I'm doing the exact same thing with all the other docker apps like jellyfin.  

By typing in the domain I've setup with nextcloud I get error code 502, bad gateway. 

This last stint of trying to fix it myself I looked at the logs for nextcloud and it says the following.

"Can't start Nextcloud because the version of the data (27.1.3.2) is more than one major version behind the docker image version (30.0.4.1) and upgrading more than one major version is not supported. Please run an image tagged for the major version 28 first."

So if nextcloud can't start I need to fix my data version problem, yes? What I've been able to come up with is I have to downgrade from version 30 to 27 in order to upgrade the data version and nextcloud can actually start working. In trying to do this I've needed to use the terminal from UNRAID or the console by clicking on nextcloud. (Hope that makes sense)

An extra few questions because of all the research I've done.

Is it better to use the UNRAID terminal? Or when dealing with a docker app, use the docker apps console? Or when should I use either?

I hope all this makes sense because I'm learning A LOT every time I dive into this stuff. 

Edited January 14, 20251 yr by Herdie27