[Connecting ETC OFFLINE editors to Vision via ARTNET]

You don't need a loopback app, both ETC and Vision should communicate without any additional software.
The one thing I have noticed with the ETC offline software is that it likes to be on a network.  It seems to work better when the software has access to a DHCP server. I've had issues trying to setup static IP addresses and get Eos to connect and have always had issues.
Be sure to enable the proper protocol in Eos and select the same one in Vision.

[Connect GrandMA to Vision 2021]

@Gabo
Please make sure you have updated to the latest version of Vision.
We fixed some issues related to the viz-key in the latest service packs.

[Connect GrandMA to Vision 2021]

Which version of Vision are you using?
Mac or Windows?
And probably most importantly, do you have the VizKey from MA?

We have identified an issue with Vision 2023 on Windows that prevents the connection.
The issue will be fixed in a soon to be released service pack.

[Connecting Vision 2.3 PC using Enttec USB PRO Box]

Enttec dmx pro drivers were dropped many years ago.

The primary interface for Vision are networks protocols like Art-Net or sACN rather than USB interfaces.