I testing out Capsman for a customer project but if the capsman server is disconnected, the managed APs also stop providing wifi.

Is there a way to make capsman only provision the APs, so if there is a power failure they will keep working or is there another way, The Dude for example?

Hope this makes sense

Dude cannot help you in this. You can choose either to use or not to use the capsman. You can have second backup capsman in the network to ensure the failover.