WPForo => Forums => Edit the forum => Adjust the color on the right.

You can choose the same color as your background or experiment with this hexadecimal color #00FFFFFF (transparent).

I also adjusted the CSS a bit by adding a margin between the node icon and the border, as well as between the block containing the title.

Adjust as needed based on your theme. On the right side, I reduced the font size and modified the calculation for the width...

@media screen and (max-width: 620px) {
#wpforo #wpforo-wrap .wpfl-2 .wpforo-forum-icon {
display: block !important;
}
}

I found the correct file and identified the relevant lines, but could you provide the class for the forum icon as well as the left border of 3px?

Thank you very much for your help mate

@media screen and (max-width: 620px)

I've installed Wise Chat, but how did you add it to the forum page?

I checked the options but couldn't find a setting specifically for the forum.😦 

You can find the @media screen formatting for all layouts in the style.css
But you shouldn't change anything if you don't know what you're doing.
Everything is formatted so that it is displayed correctly on mobile devices

As chatbox I use Wise Chat Pro, you can find the free version > here

Do you have any free plugin and what's the name of the shoutbox you use please?

While I'm familiar with how media works, could you please specify which part of the code needs to be modified to display the borders on mobile?

Thank you.

Is this normal?

yes, border and icon are removed via css

@media screen and (max-width: 620px) ..........