Beyond academic research, a non-exhaustive list of people using either Lean or related tech:

- Amazon (where they even hired the creator of Lean to pursue this)

- Microsoft (mostly cryptography but also other stuff) - ARM (hardware verification)

- Apple (hardware verification, that I'm aware of)

- Lots of companies verifying things for blockchain technologies if you're into that

- More specialised companies, e.g. Galois Inc.