'Cross-cloud chatter', 'Multicloud isn’t a (security) model citizen', all the networking primitives part (load balancers, firewalls, and delivery networks (aka DDoS protection)) of 'Time to frag your conf', as well as some parts of 'No intuitive observability' can all also be solved by NetFoundry, which is built on open source OpenZiti -
https://openziti.io/.