Having this issue on my RX 6700 XT at 3440×1440, hope the fix helps others.
———— ADDITIONAL FINDINGS ————-
Radeon Image sharpening alone is enough to fix the issue, but it was not functioning correctly under automatic Lost Ark Technical Closed Beta profile in game tab settings of Radeon software,, even if you have it enabled by default in your game tab, it does NOT work until manually adjusting the setting under Lost Ark Technical Beta Game Profile away from default or changing any of the other settings,
which is why AA enhancement appeared to fix the issue as well, it was assisting the ‘game profile’ to apply properly but it seems AA enhancement is unnecessary if Radeon image sharpening is working properly.
So in short, if you normally have Radeon Image Sharpening enabled, adjust the value under the lost ark technical closed beta game profile in the Radeon Game tab away from whatever you have it on, this is enough to get it functioning correctly & improve the…