Using second monitor on Optiplex 3280 AIO

I have a monitor hooked up to the OptiPlex, going Display Port-to-HDMI. I tried to hook up a second monitor with a USB-C-to-HDMI adapter, but monitor kept showing that it found no signal. My company's IT guy couldn't fit it or figure out the problem. I spoke to a tech support agent who had me try a dozen different things, none of which worked. He then indicated that there's only one Display Port on my PC, so the only way to hook an additional monitor would be via "daisy chaining". But, for that, I would need to get a new monitor (which I'd rather not do.)

I'm not saying the answer I got about having no option beyond daisy chaining is wrong; but, I wasn't completely confident in the person's answer. So, I'm looking for a second opinion. I can look at the back of the PC and confirm that there is only one Display Port. But, does that mean there's no other way, beyond daisy chaining, to hook up an additional monitor? Can I check my PC's specs or something to make this determination?  Is it possible a USB-to-HDMI adapter might work?