I have written a guide on how to downgrade Huawei phones to previous EMUI versions. If I am missing any method that is more efficient in downgrading feel free to comment. :
داونغريد downgrade وإزالة FRP حساب جوجل للهاتف HUAWEI MATE 10 PRO BLA-L29 اصدار 9.0.0 C432 - حلب تك - Halabtech
Downgrade EMUI 11 To EMUI 10 - How To Huawei - YouTube
Huawei Mate 10 Lite RNE L21 8.0 Downgrade Repair imei And Frp C185 - YouTube
How to roll back from EMUI 11 to EMUI 10.1 [Step by Step] - Huawei Central
Huawei's upcoming Mate 10 Pro (Blanc) might downgrade to a 1080p display - TalkAndroid.com
matte 30 pro emui12 stable downgrade to 10.0.204 for gms · Issue #162 · ProfessorJTJ/HISuite-Proxy · GitHub
Huawei's upcoming Mate 10 Pro (Blanc) might downgrade to a 1080p display - TalkAndroid.com
Huawei Malaysia releases the Mate 10 Pro on iPhone X day - SoyaCincau