Let me start by saying this is a huge issue for some of us. If you google freesync flicker you get tons of people suggesting all sorts of things but no solution. This issue has also followed me through several complete system builds with both my Vega 64 liquid and now my Radeon VII has it.
For those who dont know this is what the issue is (video is not mine)
I'm connecting via display port on an Acer XF270HU. The problem goes away as soon as you turn off Freesync just like in the video. It was suggested that its being caused by relive by a kind Reddit member.
I turned off Relive via the toggle in the Radeon console but still have the issue. What I found is if you do a fresh install of the driver and choose NOT to install relive when you click the relive section in the driver you have no Freesync flicker at all.
I know this is a decent ask for some of you with this issue but please try reinstalling your driver but dont install Relive. If this works for you please post your findings to this thread as well as report here AMD Issue Reporting Form