Paraphrased answer from @marmarek:
Basically all Intel systems support loading microcode updates from the OS, whereas only a few AMD systems do (mainly server systems and high-end workstations). However, if a vendor provides up-to-date microcode in the firmware (aka BIOS/UEFI), and you have those updates installed, then loading microcode from the OS is unnecessary. Determining whether that’s the case would require checking specific microcode versions against a table of the latest microcode versions available, which differs by CPU model. Here is the information for Intel, for example:
However, in practice, it’s probably not worth trying to check this way; better simply to install the recommended update.