NextCloud is great, but it tends to be heavyweight and packs a ton of extra functionality in.
OxiCloud may be worth considering if you are looking for something a lot lighter and faster. OxiCloud requires a minimum of 512 MB RAM, and I see it has a Docker installation too. Its focus though is very much on performance and speed.
Just note some features are still on the roadmap (which NextCloud already has) such as WebDAV support for desktop integration, basic file versioning, simple file sharing with links, etc.
It has three contributors and the code has been updated in this last week, so it is being actively developed. The project has been around for only a month, so it is also quite new, hence why those features are still to be added.