Thanks for that information. That's useful.

The device I ordered is pretty specific about being a thunderbolt 3 device with two HDMI outputs. It's not the same brand as the CableMatters one that you recommended, but it looks like it's the same class of device. (I ordered a different brand because I could get it faster.)

I'll be more careful if I ever get USB-3 type HDMI adapters to make sure they're not DisplayLink devices if I want to use them with a Mac.