In the macOS 13.1 beta (4) I was able to make it accept an ACME certificate profile. Unfortunately without hardware-bound keys nor attestation, so no Managed Device Attestation possible (yet). Hopefully that follows suit.
Linking this issue here for visibility: https://developer.apple.com/forums/thread/719032
hslatman-
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Will it be supported (soon)?
I'm also testing the ACME certificate payload. Not receiving the attestation payload in the ACME request significantly reduces the utility of the payload. E.g. there's no evidence the key is protected, no assurance this is a known Apple device, etc.