I have identically the same situation with you but without a solution yet. i haven't see also the compute mode in the latest driver for vega...
Hi, everytime I uninstalled , I uninstalled the drivers using DDU.
I think it's some driver related problem , since with the newest it works and with blockchain drivers it doesnt.
Regarding compute mode I haven't seen compute mode for vega in the latest driver.
Did they enable it ?