Question Please help me to solve this peculiar problem

@Leen Thanks for the link.
In principle, nothing else was said in the Joomla forum than here and it confirms that our answers are correct.
But I agree with the user Mr. Wimpy that these settings are a bit confusing (see here) .
Since Kunena does not have a dark mode either, I will open a ticket on Git and suggest that the other settings except from the frontend language selection and the time zones be removed.

Agree that they are confusing, and maybe better to remove, but it is a Joomla issue as well. Try to edit Joomla user profile in frontend, it is just as confusing!

But as I understand @Skywalker71 was trying to use those options to solve layout/color problems in frontend. So removing some setting from Kunena profile, won't solve the problem.
 

As far as I understand, he wanted to switch the frontend to dark mode, but Aurelia doesn't offer that.
Quote from here: forum.joomla.org/viewtopic.php?f=834&t=1015450#p3742472

This option should set the colour scheme (dark/light) of the frondend, and not the backend.
But it does not change the frontend, but instead it changes the backend colour scheme.

But you're right, if is selected dark mode in the backend doesn't solve the problem.
To solve this, we would need access to this user profile, since this error cannot be reproduced with other templates. I tested it with three different templates. But I have not tested with the Megainc template, as this is subject to a charge.

Thanks for trying to help. Actually I don't want Kunena to use any other colour except its own default colour. But, if a coloured template is used then it overrides Kunena's default template's colour and makes it unusable. I have tested with three major frameworks, T3, Helix Ultimate and Gantry. Everywhere this problem persists. As the default Cassiopeia template has no dark mode, so it will not effect Kunena. Recently I have tested this on a friend's PC who has JA Fresco template by Joomlart which is based on T4 Framework and see what happened from the screenshots:

1. With default colour:
    
   
2. With changed colour:
    
   

You can clearly see that the change in the template's colour settings are overriding Kunena's template's colours as if Kunena has no template colour at all. It should not be like this. As per my understanding, either there is a fault in Kunena's coding where it fails to protect its own template's colours from being affected by the website's template's colours or there is no such thing at all i.e protection for Kunena's own default template colours. Now, if someone buys the Blue Eagle template and it also fails to protect its colours as well, it will leave the buyers scratching their heads resulting in severe hair loss. But for me, I want the default template colours of Kunena and this strange problem has resulted my hair loss. So, what's the solution, not for my hair loss but restoring Kunena's default template colours and keeping it that way without being affected by whatever Framework or template I use ? Please help.

Blue eagle is outdated. I gave you the solution earlier:

So either adjust css, use a light JOOMLA template or look for a Kunena template that works with dark Joomla templates.

@Skywalker71
The Kunena codes are not overwritten, Aurelia is a transparent template so that it can be easily adapted to the Joomla template. In most cases, you only need a few CSS codes to customize the forum.
But it is just as easy to set up the forum so that it does not adapt to the Joomla template, as is desired in your case.
In my example, I use a light layout for Kunena again, but I still customized some things so that it harmonizes with the Joomla template (see image).
Add codes in the custom SCSS Edit SCSS | Kunena I hope this helps you. .