Confusingly, Docker now has a product called "Docker Sandboxes" [1] which claims to use "microVMs" for sandboxing (separate VM per "agent"), so it's unclear to me if those rely on the same trust boundaries that traditional docker containers do (namespaces, seccomp, capabilities, etc), or if they expect the VM to be the trust boundary.
[1]: https://www.docker.com/products/docker-sandboxes/