The holy grail microVM for me is one that can properly share a GPU across VMs, similar to what you can do with containers.
Shout out to https://smolmachines.com/ for supporting Vulkan over virtio-gpu/Venus. Currently the best implementation I'm aware of. Unfortunately my use case is running a full desktop inside the VM, and streaming it out over something like Sunshine/Moonlight. For this you need GPU rendering and video encoding. Venus rendering works, but you have to pass the frames back and forth between the host and the guest multiple times which is inefficient. Also Venus doesn't support video encode as far as I can tell.
The problem is that this feature is generally restricted to enterprise customers because VDI systems are such a profitable market. NVIDIA and AMD both only offer this on enterprise cards, and Intel has been very wishy-washy on support in their cards.
If you're looking for a thing to google, look up SR-IOV support on (consumer) GPUs.
Also if you're wondering who the customers of these things tend to be, it's generally the CAD market, law firms, etc. If no one's laptop contains sensitive data and can only stream the desktop of a remote system, the loss or theft of an employee's computer isn't nearly the same kind of a security worry.
I'm aware of SR-IOV. Widespread support would go a long way, but doesn't it require pre-slicing the GPU into discrete chunks? I want microVMs that can share share a GPU dynamically the same way they share overprovisioned CPU resources. Much more like containers.