I read that AMD microcode from the AGESA always has a higher patch version number than the microcode supplied by the kernel. The lastest microcode version from the linux-firmware repo the latest version for family 0x19 are:

Microcode patches in microcode_amd_fam19h.bin:
Family=0x19 Model=0x01 Stepping=0x01: Patch=0x0a0011d1 Length=5568 bytes
Family=0x19 Model=0x01 Stepping=0x00: Patch=0x0a001079 Length=5568 bytes
Family=0x19 Model=0x01 Stepping=0x02: Patch=0x0a001234 Length=5568 bytes

My CPU (Ryzen 5900x) reports [ 0.579161] microcode: CPU0: patch_level=0x0a20120a, though? My BIOS is from January, the amd-ucode was update in July.

Others have come to the same observation and speculate that the linux-firmware microcode is only for Epyc. AMD in their statement about inception only talks about updating microcode via AGESA.

https://www.phoronix.com/forums/forum/phoronix/latest-phoronix-articles/1402527-amd-inception-cpu-vulnerability-disclosed?p=1402567#post1402567
https://www.phoronix.com/forums/forum/hardware/processors-memory/1349645-amd-publishes-new-family-19h-cpu-microcode?p=1349760#post1349760
https://www.reddit.com/r/archlinux/comments/hdrron/amd_microcode_not_loading/

Anyone having more information on this?