DigitalOcean Load Balancers will set some HTTP headers that pass the source IP through to your backend servers, like CloudFlare does with X-Forwarded-For, and CF-Connecting-IP headers.

From the Protocol Support section of the docs:

The load balancer sets the X-Forwarded-For, X-Forwarded-Proto, and X-Forwarded-Port headers to give the backend servers information about the original request.

So that’s one way to access the client/source IP information for an incoming HTTP request.

Another is to use the PROXY Protocol support that’s built in - but there you have to make sure your backend servers support it, otherwise the Load Balancer will mark them unhealthy.