In reading your post I'm sensing that you may be misusing domains in the Holacracy sense. A domain is a piece of organizational property that can be given to a role to restrict or authorize access to that property. In what I've read there doesn't seem to be a domain around the type of technology or architecture unique to any role.
One thing to consider, while the Lead Link holds undifferentiated work of the circle like deciding architecture and technologies right now until it gets split into a separate role. Which if the work of that is ongoing the Lead Link should be bringing that tension to make it clearer. Equal to the point you can propose another role to make those kinds of decisions or create a policy granting that authority to decide those things for any role that needs to.
Hope this helps.