No ROM will restore Widevine L1 . You will watch Netflix in SD (540p). Also, the M-Pencil stylus may lose pressure sensitivity.
Installing a custom ROM on the Huawei MatePad 10.4 is significantly more difficult than on most other Android tablets due to Huawei’s strict security policies and locked bootloaders huawei matepad 104 custom rom install
Huawei terminated its unlock code service to "achieve a better user experience" and enhance security. Without this code, the fastboot oem unlock command will not work. No ROM will restore Widevine L1
Have you successfully installed a GSI on your MatePad 10.4? Share your story in the comments below. huawei matepad 104 custom rom install
Due to the closed nature of Huawei’s hardware (Kirin chipsets), developer support for custom ROMs like LineageOS or Pixel Experience is virtually non-existent for the MatePad 10.4