On Intel machines and windows, the TEE is Intel SGX for some DRM implementations (not necessarily widevine's).
(IIRC, unsubstantiated) Windows clients use Windows’ DRM implementation, not WideVine.
Chrome and Firefox use Widevine DRM at L3 (software implementation). Edge and IE use PlayReady (which has support for hardware DRM, optinally selectable by the app/website).