Post installation

Just a couple of years ago, I managed to build a view that showed me content filtered by ‘parent term’ from a specific vocabulary.
Now, in version 10.6.7, it seems impossible to do.
Have there been some new limitations, or have I completely forgotten how to do it?

For example, filtering all content that has terms whose parent is “economics” in the “arguments” vocabulary

I would be very grateful to anyone who can give me some guidance on how to achieve this result

According to your schedule there seems to be no way of avoiding upgrading every 6 months in order to remain in support. Example;
Currently, everyone using Drupal would be on v11.3 or lower.
June to December: upgrade to v11.4 between June and December.
December to June next year: if support for v11.4 ends December (currently no advised date), then you have the options of upgrading to either v11.5 or v12.
When you are responsible for multiple Drupal sites, this continual need to upgrade every 6 months to remain in support is problematic. 

Currently there is no information available here Drupal core release schedule | Core release cycles | About guide on Drupal.org about when support will end for Drupal v11.4. Please can that be made available as soon as possible.

Historically I am using other wysiwyg html editors (hacked in many ways to suit my requirements). However now I wish to start using ckeditor5. 

I understand ckeditor5 is way different than other wysiwyg html editors (no execCommand for example)

So I want to try it while my existing editors are still working. Once I am good with ckeditor5, I will make a switch.

So the question

Is it possible to use existing ckeditor5 that comes with core, without actually enabling the module.

My webhotel offers only Plesk. People who know composer have advised that using composer needs access from Plesk to operation system prompt.
I have updated minor Drupal 11 versions using old style uploading zip file and copying new files from the zip.

Now I should update Captcha and Forum modules but have found only composer  instructions.

I have never used composer.

Are there any means to update and upgrade Drupal using Plesk?