Can't edit my comment (#2) so I just wanted to correct the sentence "That's (most likely) the reason why the official HAProxy docker image builds on Alpine Linux which uses Open RC as init system.". The official HAProxy Docker image runs on Debian but also supports Alpine Linux. The big difference there: They don't install HAProxy from a deb package but rather build HAProxy from source (during image build).
Can't edit my comment (#2) so I just wanted to correct the sentence "That's (most likely) the reason why the official HAProxy docker image builds on Alpine Linux which uses Open RC as init system.". The official HAProxy Docker image runs on Debian but also supports Alpine Linux. The big difference there: They don't install HAProxy from a deb package but rather build HAProxy from source (during image build).