According to MSI Support BIOS Download page only the Ryzen Bristol Ridge (APU) processors are not supported above BIOS version 7B89v17: https://www.msi.com/Motherboard/support/B450M-MORTAR#support-cpu
But after BIOS version 7B89v19 that warning is not mentioned anymore. So not sure if that means that BIOS version v19 and above still support Bristol Ridge APUs or not.
Doesn't mention anything about Pinnacle Processors (2xxx) not being supported. So you should be able to update your BIOS to the latest version.
But to be safe I would ask MSI Support to verify that information.
NOTE: Before updating your BIOS version to the latest make sure you update FIRST your Motherboard's CHIPSET either using AMD CHIPSET or MSI CHIPSET driver, whichever is newer.