See the API documentation on load balancers for more information.
doctl documentation on load balancers for more information.
If you enable PROXY protocol on a load balancer, but the services on the backend Droplets aren’t configured to accept PROXY protocol headers, those Droplets will give a 400 response to the load balancer’s health checks. This means the load balancer will consider them unhealthy and will stop routing traffic to them.
How you enable PROXY protocol support on your Droplets depends on the software you’re running. Here are some resources for common services: