Connection Logitech X-530 via Mac Mini M2 headphone jack

I've been using Apple products since 2005, and I've been using the same audio setup for almost as long. Until recently I had the Logitech X530 connected via the audio out jack of my 2013 iMac 27". No issues.

I upgraded to the M2 Mac Mini. When I try to connect via the audio out jack, I have no sound out of any speaker. I have tried connecting via an amp and also via usb-c adapter. The Mini shows the option for the external speakers in the Sound menu (and also in the Audio MIDI Setup), but I get no sound out of any speaker. Volume is turned up on the system and on the speakers. The speakers are on. I've restarted several times now to no avail.

Now here is the really strange part: if I plug headphones into the headphone jack on the X530 itself then I get sound via any of the 3 setup options I mentioned above: when the X530 is plugged directly into the headphone jack, when using an amp, and when plugging into a usb-c port with an adapter.

So the X530 appears to be working and the signal is being passed through the system somehow, but I am at a complete loss as to why I'm not getting any sound of out any of the speakers. I am not having any luck setting up a multi-channel output device using the Audio MIDI Setup, but I didn't have to do this before.

Has something changed with the audio out signal that renders the X530 obsolete? If so, why is there still sound when I plug into the headphone jack on the main speaker unit?

Any help would be appreciated.