Sccm is too big. I don’t think you’ll find an all in one alternative.

Piecemeal is easy though. Wazuh for inventory. Chef or ansible for packages and desired state config.

Lots of pxe boot deployment options, including wds, which sccm pxe is built on.

Maybe tackle one feature at a time and pose your questions one at a time, so people doing pxe boot imaging can chime in on that specifically for example.