We are continuously working on optimising the game. It is possible that along with our optimisation tweaks and game engine updates in the future, the performance on these video cards will improve. However, we can't promise that this will solve the issue as it is related to old Radeon cards that have been not receiving updates since 2015/16.
Additionally, the following workaround may help for GOG GALAXY:
1. Go to the GWENT installation folder
2. Right-click on the "Launch Gwent" shortcut and click Properties
3. Under the Shortcut tab, click on the "Target" input field and add the following text at the end: -force-feature-level-10-1
4. The input field should look similar to this: "C:\Program Files (x86)\GOG Galaxy\Games\Gwent\Gwent.exe" -force-feature-level-10-1
5. Launch the game through GOG GALAXY
If you are playing on Steam, then this workaround may help:
1. Right-click on GWENT under the 'Library' in Steam and select 'Properties'
2. Under the 'General' tab click the 'Set launch options...' button
3. Enter the following launch options: -force-feature-level-10-1
4. Close the game's 'Properties' window and launch the game through Steam