That’s an app which sadly is not available on iOS

I think it’s quite limited in features, especially for connecting to NAS. It doesn’t support ubiquitous protocols like, WebDAV, sftp, ftp… this reason alone makes it unusable for me.

Completely true, but I don’t think Apple wants people to be able to easily manage their files on their iPhone, I don’t exactly see the reason. but it’s probably something to do with Mac sales.