I like the idea of multi-cloud very much, kudos to the author for pushing for it. One crucial issue that isn't addressed by a hexagonal architecture however is

I like the idea of multi-cloud very much, kudos to the author for pushing for it. One crucial issue that isn't addressed by a hexagonal architecture however is data egress charges. Data egress is the gravity of the cloud services world, and it's are an insurmountable barrier for many services. The moment you start planning a multi-cloud deploy, and start looking at shifting services that are tightly coupled, or require data replication (databases, logs, storage) between clouds, you're going from low or no cost data charges, to paying egress on -both sides- of every transaction. I know first-hand that these costs can quickly out weigh any disaster recovery / eggs in one basket argument you might put forward. It even dominates an "this cloud provider will probably be our competitor in 2 years or is our competitor right now" argument, and my guess is data egress has strongly contributed to companies like Netflix continuing to use AWS.