Here is an RX590 - It has the Compute Option.
Sorry for the del;ay in replying.
Just spent 2 days trying to get AMD Drivers to install on Windows 10 Pro 2004 on new SSD.
It looks like that Compute versus Graphics option is only there for Fiji and Polaris GPUs.
The above screenshot is with Adrenalin 2020 20.9.1 installed on Windows 10 Pro 2004 with latest updates.
I hope that answers your questions.
I cannot confirm that. I have a 3 GPU Workhorse with 3x RX580 and the most recent Windows 7 Adrenaline Driver installed.
I cannot select "Custom" so I cannot get to the required view to be able to select compute mode.