ucode-amd from home:Simmphonie:surface:stableBackport project
Select Your Operating System
Add repository and install manually
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Simmphonie:surface:stableBackport/15.6/home:Simmphonie:surface:stableBackport.repo zypper refresh zypper install ucode-amd