You may be surprised but a private (self-hosted) torrent tracker is how I did this when I had crappy internet and had to send over a bunch of pictures and video to family.
You can encrypt the data before sending, although it still should be fairly safe, speeds don’t matter much, there’s no storage to pay for or risk leaking.
I can confirm caddy is more of a high availability proxy than a proper load balancer, but it does it’s job and has an api you can hook up to a gui if you want. Or like I do - to a config repo with ci/cd deployment.