What is going to work, Which DisplayLink do I purchase?

[a-romerr]

What model should I purchase? Does DisplayLink even support this basic/simple configuration anymore?
I need help choosing the correct DisplayLink.

To DATE:
I have tried two different DisplayLink models, and neither has worked when trying to get Port1 HDMI to transmit a signal.
The first was a Pluggable UD-6950PDZ Triple 4K Monitor Dock. I failed to get Port 1 to transmit and returned the item to Amazon as defective.

I currently have the UD-3900PDZ purchased through Amazon.ca, which I will be returning as I just cannot get Port 1 to transmit an HDMI signal, no matter what I try. Is it defective? I'm not sure this time, as this is the second purchase, and I cannot believe my luck would be that bad.

HISTORICALLY:
I still have a 2-port HDMI/DisplayPort 4K capable Display link, Model UD6950H, which just worked.

WHAT I REQUIRE
I am looking for a similar "It'll just work Display link, but three ports HDMI/DisplayPort with at least one port being 4K capable.

MY SETUP
COMPUTERS
Three computers = 2 Windows and 1 MacBook M1.

MONITORS
Mobile Pixels Geminos X, Dual LCD monitor, 24"
2560 x 1440 QHD @ 75 Hz
IPS
2xHDMI, 2xUSB-C

Samsung U28e590
Desktop Mode: 4K UHD (2160p) 3840x2160 at 60Hz
2xHDMI 1xDisplayPort

CONNECTIONS ARE DONE THIS WAY
All connectivity from Monitor to DisplayLink will be through HDMI
All connectivity from PC to Displaylink is USB 3.0 via a USB 3.0 4 port KVM
(to allow me to switch between PC's/MacBook)

This connection setup worked just fine with the 2-port Displaylink,
When I moved to 3 port and with the HDMI port one not working on the Display link, I substituted in an old school HDMI KVM to manage the 3rd screen
It is a convoluted setup, so I want a 3-port DisplayLink to work. Please...

I'm certain the issue with the current three-port I purchased has to do with this "Alt Mode" on HDMI port 1.

I want a simple 3-port DisplayLink that will work with USB 3.0 inputs OR USB 3.0 to USB C adapters, depending on the configuration required.

What model should I purchase? Does DisplayLink even support this kind of basic/simple configuration anymore?