I recently moved Nextcloud and Gitea from Containers on a Debian VM to Alpine LXCs running Alpine's packages. I've never had Nextcloud's web interface so snappy and my resource usage for both is next to 0.
If you're running Proxmox I'd highly recommend trying out Alpine LXCs if they package your services.
I'm assuming you installed it directly to the container vs running docker in there?
I have been debating making the jump from docker in a VM to a container, but I've been maintaining Nextcloud in docker the entire time I've been using it and not had any issues. The interface can be a little slow at times but I'm usually not in there for long. I'm not sure it's worth it to have to essentially rearchitect mely setup for that.
All that aside, I also map an NFS share to my docker container that stores all my files on my NAS. This could be what causes the interface slowness I sometimes see, but last time I looked into it there wasn't a non hacky way to mount a share to an LXC container, has that changed?
Yes, Alpine maintains Nextcloud in their repos.
I mount my NFS share to the Proxmox host (you can mount using the gui and set it to any form of storage you want) then bind mount the share folder to the LXC. I moved from docker in a VM to this LXC with no disruption to my data.