The HTTP header does contain the following information: button-serial-number; button-battery-level; button-name. I agree it would be nice if it also included the button-action. I just put the info in the URL (eg flic/1/click) so I don't have to set a body. I then handle this in Node Red where I can specify the endpoint as flic/:from/:action and it pulls the parameters out for me automatically.

I would categorise Node Red as a replacement. I've always had mine set up this way, where the flic buttons all do "internet" requests along the lines of "http://192.168.0.18:1880/flick/4/click". Node Red then has an http-in node that picks this up and does something with it. In my case, it controls things in Home Assistant, but Node Red has add-ons for Smartthings and can control devices directly too.