Hello, thank you for your feedback. I understand your frustrations on getting the theme feature to work on your messages and I will be more than happy to take a look at this with you.
Galaxy themes will change the appearance of your Home screen, Apps screen, icons, and wallpaper. There are a few things that can cause the theme to not apply correctly in addition to having dark mode applied.
If a theme was installed incorrectly, it will only be partially applied. Use the following steps to solve this issue:
Apply the default theme to your device. Touch and hold an empty area of your Home screen, and then tap Themes. Tap Menu (the three horizontal lines), tap My stuff, and then tap Themes. Tap your default theme, and then tap Apply. Next, delete the theme that was installed incorrectly. Tap the Delete icon, then tap the theme, and then tap Delete. Navigate back to the theme and download it again if desired.
In addition, check if there is an update available for the theme in question. Themes can only be updated if the seller has registered an updated version. Use the following steps to update your theme:
Touch and hold an empty area of your Home screen, and then tap Themes. Tap Menu (the three horizontal lines), tapMy stuff, and then tap Themes. Tap the desired theme to check if an update is available and then tap Update to proceed.
Check to make sure you do not have it set to Dark Mode. Themes do not work well with Dark Mode.
Also, be sure you are using Samsung Messages. No third-party message app will theme.
