How can I send proxy protocol with apache ProxyPass

Question

I am currently using apache as a reverse proxy ('sending') to another apache server ('receiving')

I want to enable the ProxyProtocol between these 2 servers

On the receiving end I can 'enable' proxy protocol simply using mod_remoteip (https://httpd.apache.org/docs/2.4/mod/mod_remoteip.html#remoteipproxyprotocol)

But how do I make the sending apache server implement it? I am using ProxyPass for regular HTTP(s) traffic and RewriteRule with [P] for WebSockets:

<VirtualHost *:443>
    ServerAdmin webmaster@localhost
    ServerName x.y.z

    SSLEngine on

    SSLCertificateFile    /etc/letsencrypt/live/xyz/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/xyz/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/xyz/chain.pem

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    RewriteEngine On
    ProxyPreserveHost On

    RewriteCond %{HTTP:Upgrade} =websocket [NC]
    RewriteRule /(.*)           ws://receiving-host/$1 [P,L]

    ProxyPassMatch ^/.well-known !
    ProxyPass / http://receiving-host/
    ProxyPassReverse / http://receiving-host/

    RequestHeader set "X-Real-IP" "%{REMOTE_ADDR}s"
    RequestHeader set "X-Forwarded-Proto" "%{REQUEST_SCHEME}s"
</VirtualHost>