It’s pretty easy to move files on and off the iPhone using a usb/portable ssd and the files, hardest part would be you need a usb to lightning otg cable which is somewhat uncommon.

It’s the kind of thing you don’t really do if you follow the apple flow though. You’d either stream the video from whatever service, or you sync it with apple photos and it will be available on your phone.

When I plugged in the iPhone via cable to my Windows PC, I could only extract pictures which were taken recently, god knows why.

Apple officially recommends to install iCloud on the PC and download the files from there, but they didn't let me disable the upload of the files on my PC, so I uninstalled iCloud again.

Then the recommendation was to just download it from iCloud Web. Which I did. But for some reason iCloud download default to a lower resolution (720p video in my case) instead of the full resolution. To do this I had to click on a small button, which then gave me the option to download my own files in full res.

Of course I only noticed that I'd downloaded a lower res after editing a video for 5 hours. All in all, an extremely subpar experience. Every Android phone ever can just transfer files over cable to any PC, for some reason just iPhones have to be complicated...