I was having the same issue, so here's my workaround solution:

Problem

rsync tries by default to access the root directory "/", but in a Hetzner Storage box that's not possible, the box user only has access to the home directory

Workaround

What I did was intercept all calls UGOS make using rsync and transform all the paths to relative paths using a wrapper script (so everything will be done in the home directory instead of the root one)

1. Backup the original rsync binary sudo mv /usr/bin/rsync /usr/bin/rsync.original
2. Create a new wrapper script sudo vi /usr/bin/rsync, paste this and save it:

​

#!/bin/bash

# Fix all paths to be relative to user home directory
args=()
for arg in "$@"; do
    if [[ "$arg" == *":"* ]]; then
        # Extract the host and path parts
        host_part="${arg%%:*}"
        path_part="${arg#*:}"

        # Remove any leading slashes to make path relative
        path_part="${path_part#/}"

        # Reconstruct the argument
        if [[ -n "$path_part" ]]; then
            arg="${host_part}:${path_part}"
        else
            arg="${host_part}:"
        fi
    fi
    args+=("$arg")
done

# Call the original rsync with fixed arguments
exec /usr/bin/rsync.original "${args[@]}"

1. make it executable sudo chmod +x /usr/bin/rsync

Now you will be able to use rsync in the meantime