Soeaker

I don't think most motherboards these days come with a built-in buzzer.
They still have a speaker connector (SPK_PLED) if you insist on connecting to a case speaker/buzzer.

If you really need a buzzer, you can buy something like:
https://www.amazon.com/dp/B01DM56TFY/
(Not endorsing that particular device. It's just the cheapest one that came up when I searched)

None of the motherboards I bought in the last 5 years or more came with a separate buzzer.

Oddly enough, one motherboard I bought actually has a built-in buzzer. X470D4U. I guess the buzzer accounts for the $250 I paid for it. (laugh)

Note, I'm talking about the PC buzzer/speaker here. Almost nobody uses it these days. I'm not talking about soundcard audio. Most motherboards have built-in audio chip (almost always Realtek something or rather). You can hook up to it using a standard 3.5mm jack.

old AT cases had PC speaker included, some mainboards may have soldered speaker, but mostly you get no speaker, you do have option to add it (very cheap buzzer) as mainboard has connection for it, but since mainboard have now debug leds/debug codes, speaker may not be necessary