I had the same issue. #hex is not optimised for One UI 6. I applied the default theme back and removed #hex for now as its incompatible with the current version of One UI.
Initially for me as well themepark and galaxy themes were not working. I found a fix which helps to revert back to the galaxy themes.
Note: Themepark will still not work as Good Lock is yet to be optimised for OneUI 6. As per blogs it will be released alongside the stable OneUI 6.
Steps to follow: 1. Download a Universal Android DeBloater such as this - https://github.com/0x192/universal-android-debloater 2. Turn on USB debugging on your phone and install samsung USB drivers on your PC. 3. Next, check if the package - com.samsung.android.themestore is installed and enabled (it should be in most of the cases). If not go to Settings -> Apps -> search for Galaxy Themes -> Clear cache and Data -> Click Enable. 4. Connect your phone to the PC and set it to the transfer files and media mode. 5. Open the debloater application. 6. In the debloater app, you will find filters to sort the application packages on your phone. 7. Select the filter that shows Disabled packages and you will find - com.samsung.android.themecenter. 8. Re-enable the above package as its responsible for displaying the galaxy themes app UI and is disabled by #hex for its smooth functioning. 9. After following the above process. Disconnect your phone from PC and try the galaxy themes app. It should work now as usual.
