I don't think it's a concept that meaningfully exists. Microkernels are primarily concerned with isolating non-executive functions (e.g. device drivers) for stability and/or security (POLA) reasons. NT achieves virtually none of that (see e.g. Crowdstrike). The fact that Windows ships a thin user-mode syscall shim which largely consists of thin-to-nonexistent wrappers of NtXXX functions is architecturally uninteresting at best. Arguably binfmt_misc would then also make Linux a hybrid kernel.