I think the easiest way is sftp over tailscale, works over any distance, easy enough to setup, plenty of apps, ish for an iphoneterminal apk add openssh (idk how to dload there but you should be able to, can convert files locally using ffmpeg off an iphone, pretty great), termius/termix/neoserver for a more "modern" way to connect into the terminal and sftp. I prefer apps with a terminal jic I need to use it to convert something real quick on my pc.