The Huawei Mate RS users are reporting that they received the latest January 2020 security patch EMUI 220.127.116.116 (C721E9R1P11) update. This update is based on EMUI 9.1.
The latest update only includes the January 2020 security patch update with the size of 235 MB. You can download it from your system settings option.
Earlier, Huawei P20 Lite users also got a chance to get the January 2020 security update. The changelog is the same as Huawei Mate RS.
Download Huawei Mate RS EMUI 18.104.22.1686 update via Settings > System > Software update > Check for updates.