For anyone who wants to disable the vulnerable primitives, I just made a bash function:

  #!/bin/bash

  # Function to apply Terrapin Mitigation to SSH configurations
  terrapin_mitigation() {
    echo "Applying Terrapin mitigation to SSH client and daemon config..."

    # Function to filter algorithms, reading from stdin
    filter_algorithms() {
      while read -r alg; do
        if [[ "$alg" != *"chacha20-poly1305@openssh.com"* ]] && [[ "$alg" != *"-cbc"* ]] && [[ "$alg" != *"-etm@openssh.com"* ]]; then
          echo "$alg"
        else
          echo "Removing vulnerable $alg" >&2
        fi
      done
    }

    # Ensure .d directories exist
    sudo mkdir -p /etc/ssh/sshd_config.d
    sudo mkdir -p /etc/ssh/ssh_config.d

    # Get and filter algorithms
    kex_algorithms=$(ssh -Q kex | filter_algorithms)
    ciphers=$(ssh -Q cipher | filter_algorithms)
    macs=$(ssh -Q mac | filter_algorithms)

    # Create configuration lines
    kex_line="KexAlgorithms $(echo "$kex_algorithms" | tr '\n' ',')"
    cipher_line="Ciphers $(echo "$ciphers" | tr '\n' ',')"
    mac_line="MACs $(echo "$macs" | tr '\n' ',')"

    # Remove trailing commas
    kex_line=${kex_line%,}
    cipher_line=${cipher_line%,}
    mac_line=${mac_line%,}

    # Output to sshd.d and ssh.d files
    echo ""
    echo "*** /etc/ssh/sshd_config.d/terrapin-mitigation: ***"
    { echo "$kex_line"; echo "$cipher_line"; echo "$mac_line"; } | sudo tee /etc/ssh/sshd_config.d/terrapin-mitigation
    echo ""
    echo "*** /etc/ssh/ssh_config.d/terrapin-mitigation: ***"
    { echo "$kex_line"; echo "$cipher_line"; echo "$mac_line"; } | sudo tee /etc/ssh/ssh_config.d/terrapin-mitigation
    echo ""

    echo "Terrapin mitigation configuration updated!"
  }

  terrapin_mitigation

Because of the way SSH resolves its config (first of CLI, user local, system wide), in some cases you may prefer to alias ssh to configure this at the command line.

Also disabling some algorithms might bar you from connections that are limited to those. I'm not an expert, this is just what I threw together now. You're welcome to use it unless you know a better way. Please suggest improvements if you see them and use at your own discretion otherwise! :)