Is there a trade-in value for the Mac mini w/M1 chip

No. Apple typically doesn't offer trade-in values for current models, but there will be a quote for the M1 Mac mini as soon as it is replaced by a newer model. If you're looking to upgrade to a different computer, I would suggest selling your computer secondhand or holding onto it until Apple quotes the M1 Mac mini for trade-in.

You could get a used Thunderbolt display. It has a camera, speakers and extra ports.