Remote Screen Sharing on macOS is actually just VNC on port 5900. It's insecure by default - intended for local network sharing. Here's how you enable it and share it via ssh:

1. Turn on Screen Sharing on the Host (the computer you want to connect to)
2. Edit ~/.ssh/config on the Guest (the computer you connect from) to forward ssh over 5900

   Host foobar foobar.local
       LocalForward 5900 localhost:5900
   

3. Connect via ssh from the Guest to the host

   ssh foobar.local
   

4. Open Finder on the Guest and hit Cmd ⌘ + K or select Go => Connect to Server
5. Connect to localhost (where the ports are forwarded locally)

Also of interest:

• Access web pages through your home network via SSH
• How to Mirror Your iPhone Screen to Mac
  • Connect iPhone via USB
  • Open QuickTime, New Movie Recording
  • Select iPhone as video source

My personal setup

I have mine set up to work locally or over the internet.

Here's my ~/.ssh/config (also includes a SOCKS5 proxy):

#
# Hostname aliases
#

Host foobar
    Hostname foobar.local

Host foobar.ip
    Hostname foobar.duckdns.org

#
# Host-specific config
#

Host foobar.ip foobar foobar.local
    User myusername
    # macOS Finder's built-in VNC Screen Sharing
    LocalForward 5900 localhost:5900
    # Socks Proxy
    DynamicForward 6789

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