So, I've installed Displaylink on the 27" iMac (version for Sonoma: 1.12.4 ). When I attempt to install it on the 2009 iMac that is the monitor (versions for High Sierra: 4.3.1 or 4.1), it all installs as normal, but the application is not in the applications folder, only a folder with the uninstall app. If I try to reinstall, I get a warning message saying that it is installed. Thoughts?

I'm using a late 2009 21.5" iMac as an external monitor from Duet software, from my 2019 27" iMac. I run a MacBook Air M1 as a third screen (second Monitor) also using Duet, but with different software for the later models. I'm dong this because I can't get TDM to work, either because it requires a 27" iMac or because I have the wrong System (Sonoma not Catalina). However, Duet generally works well, but I'm getting some latency and high CPU temps when I do some more complicated things, like attempting to share documents on Teams from my "monitor". I wondered if there was a solution that offloaded some of the processing, and I already have an OWC Dual HDMI Displaylink USB-C device for my M1 MacBook Air, so I thought I would give it a go. I have a USB-C to HDMI female cable, to which I added a HDMI Male to Mini-Displayport Male Cable. So, I install the Displaylink software on the 27" iMac, approve the Screen and System Audio Recording System Settings. Then I connect my Displaylink device, including the cable to the older iMac and I get:

"Please Connect your Displaylink Device"

In the icon at the top menu on my main iMac.

So, like Loukas, my "iMac display does not switch to iMac 27"".

Thoughts?

I tired Wavlink 5k usb-c hub with iMac 2012 and TDM didn't work :(

I'd like to know as well.