A few years (!) ago, I wrote about using accessing your files from anywhere using a custom DDNS setup. In the 2 years I've been in Chicago so far, my entire apartment building has shared one IP address. That meant my custom DDNS solution couldn't work anymore, and so I looked into other ways I could access my files from anywhere. I couldn't find any.
There are things like ngrok that can expose local servers through tunnels, but that wouldn't work for my on-demand use case where I'd remotely turn on my computer to access files through SMB.