You say free software and of course, it's nice to have source code and flexibility.
I have nothing against licensing and it looks like things are moving there. Do you have a recommendation for Metal / DirectX support for that kind of rendering facilities? What matters more for me is performance.
Slug has DirectX support (it runs on all major APIs). Pathfinder does not yet, but likely will in time. As always, evaluate the offerings and choose what meets your needs best. Performance is probably comparable between the two, but that depends hugely on workloads and how it's integrated into the rest of your system.
I have nothing against licensing and it looks like things are moving there. Do you have a recommendation for Metal / DirectX support for that kind of rendering facilities? What matters more for me is performance.