buildroot has defconfigs for building uefi or bios images capable of booting on most any hypervisor. you can easily extend them. you can also easily strip them

buildroot has defconfigs for building uefi or bios images capable of booting on most any hypervisor. you can easily extend them. you can also easily strip them down and get itty bitty tarballs suitable for import as a docker container images https://github.com/br-containers/br-containers https://github.com/br-containers/br-containers