🇮🇱Israel @taitai

This issue is very alive, I am on Drupal 10.3.6
It does not matter what display mode you set, you always get the default display mode.
Very simple to recreate:
Create a view page of one content type
Format: Unformatted list
Show: Content
Choose any view mode
Look at the results
Change the settings view mode
The results do not change
Access was set to unrestricted

Your #4 works fine, thanks.
However...2 questions:
1. Why do you need to set the format explicitly as the field itself already defines the allowed format
2.  I used the following which did not work..
$Node->field_design_abstract = $abs_items;
$Node->field_design_abstract->format = 'full_html';

Code:

// Set the abstracts array
foreach($abstracts['abstract'] as $key => $abstract){
$abs_items [] = '

Insight ' . $ins_items[$key] . '

' . $abstract;
}
// Set the field
$Node->set('field_design_abstract',$abs_items);
$Node->save();

taitai → created an issue.

Closing, it is a problem in my system with widgetbase.php

taitai → created an issue.

Your code is only partly correct

It shows the TD alright but it does not show the label. 

If you choose the tablesaw-stack as your default mode it will include a TD that shows the label and another span that shows the content.
If you choose tablesaw-columntoggle as your default mode and you modify the attributes, as shown in your code, it will only include one TD with the content. Missing the label.

taitai → created an issue.

I have found a temporary fix. Do not bother to send a format patch.

tb_megamenu.theme.inc

commented out:
vars['link']['title_translate'] = htmlspecialchars_decode(Xss::filter($title));

Added:
$vars['link']['title_translate'] = $title;

This has fixed my problem.

taitai → created an issue.

I am on 2.0.0-alpha7 and the same problem still exists