You can definitely add uncertified accessories (using CSA test Vendor ID 0xFFF1) to HomeKit via an "Add Anyway" confirmation. Because Apple tends to be extremely conservative about this kind of stuff, I'd expect that all systems that support Matter would allow this.
(1) https://tomasmcguinness.com/2025/06/27/matter-building-a-tin... (2) https://tomasmcguinness.com/2025/06/30/matter-tiny-dishwashe...
You can definitely add uncertified accessories (using CSA test Vendor ID 0xFFF1) to HomeKit via an "Add Anyway" confirmation. Because Apple tends to be extremely conservative about this kind of stuff, I'd expect that all systems that support Matter would allow this.