GNU Hurd for example. I haven't used it so I'm not sure of the exact status but it sounds like they are using it in some cases to make use of existing drivers

GNU Hurd for example. I haven't used it so I'm not sure of the exact status but it sounds like they are using it in some cases to make use of existing drivers in a microkernel style. There have been a few attempts to rumpify Linux but it doesn't seem like any of them succeeded and I'm not sure if anyone is still trying.