Unikraft (https://unikraft.org/) started as a Xen Project and has supported Xen since the very beginning. We are now improving the Xen support. We have Unikraft running on Xen ARM64, we are now working on getting Xen integrated with the companion CLI tool KraftKit (https://github.com/unikraft/kraftkit). And to run binary compatible applications (https://unikraft.org/docs/concepts/compatibility) with Xen.
At the same time, we are looking forward to get a better connection between the two projects, such as running QEMU as a unikernel target. This is part of a discussion we are having on Matrix with Andrew Cooper, avallejo and others.