Hello Janluc,
Thank you for reaching out to Plugable Support!
I am sorry to hear that you are running into issues with your TBT3-UDZ, but I would be happy to help diagnose the issue.
Unfortunately, our TBT3-UDZ will not work with a USB-C to USB-A adapter, as the dock needs to connect to a Thunderbolt 3 or Thunderbolt 4 port on your computer for full functionality. The reason that this setup worked on your previous Dell dock was because that dock only required a USB 3.0 connection, similar to our UD-6950H docking station.
Looking at the specifications for your laptop, the Dell Latitude 3580 does not have a Thunderbolt 3 or Thunderbolt 4 port, so we unfortunately do not expect this dock to work with your device.
Sorry for the inconvenience! Please let me know if you have any other questions.
Thank you,
Evan
Plugable Technologies
www.plugable.com/support