For windows, you can create an Azure DevOps account/team for free, and create pipelines against your Github codebase for Windows builds. You'll probably have to install extra pre-requisites for your build though, not sure what's actually in the box, using custom windows agents at work, or linux/docker targets mostly.
It's (Azure DevOps) not always the easiest/best, but it's pretty good... my preference when including the project mgt tools.
I've been looking for distrbution mechanisms for a while now, and static binaries are not easy for applications with a GUI.
As for Metal, it just works better currently with the underlying libraries I'm using (GLFW + gfx-rs), than MoltenVK.