I use sftp with either termux on android or ish on ios, alternatively telegram or email.

Edit: I don’t use it, but if I’m not mistaken, nobody mentioned any cloud service.

And before I discovered ish, I used the python html module to start an html server and connected with safary. You shouldn’t do this when your connected to the wild, open internet - it opens up the device on which your server runs for everybody unless you invest the work to secure the html server, taking a 1min research 1 line task into real work.