As long as the CVO router which I believe are ISR G2 routers supports redirection/dACLs etc, I don’t see why it should not support posture. So the real question is, do they support redirection/dACLs/CoA and redirect ACLs? I’ve skimmed through Cisco feature navigator for 891 ISR G2 Image 15.7(3)M train and I do not see the features required for Posture. So I do not believe you can do so but again, I’m not an expert on ISR routers. If you have any local setup, probably try setup it up and see if the attributes being sent from the ISE server are being applied on the interface to which the client connects to.
On the other hand, you could try posture without redirection which removes the dependency over the network device that the endpoint is connected to except for CoA (one of the features that I did not find this IOS supporting on these routers but not 100% sure). Check it out here :
https://www.cisco.com/c/en/us/support/docs/security/identity-services-engine-22/210523-ISE-posture-style-comparison-for-pre-and.html
