Drupal 8.x

I am using a Taxonomy called "Location" https://prnt.sc/1ucz8fh as reference field in User account fields https://prnt.sc/1uczg8c. Now requirement is Add Other options for Cities

I just manually installed Drupal 8.9.19 on a remote server. The installation process went through, but the Bartik theme does is not working. When I try to click on any of the links (Content, Appearance, etc.), I get an Internal Server Error: 

"The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

When a user tries to write a new comment for any node, and hits preview button, she gets Page Not Found error (404)

This happens only when the comment is new (not already in db)

This does not happen if one is editing existing comment and hits preview.

Moreover ...

Surprisingly this did never happen on my development site. .... but is happening only in production site.

Can you give me any clue where should I start looking for issues and how.

Thanks

MAC OS Bug Sur 11.5.2
Drupal 8 via ddev

-- installed docker for MAC desktop [but get a FAIL: unable to find docker executable on PATH when I run Docker's diagnostic tool]
-- yet successfully set up ddev drupal 8 container as per instructions on drupal site
-- able to install several modules using ddev composer require/then enable using ddev drush en [module] -y [modules like pathauto, admin toolbar]. I've been doing a ddev drush cr and ddev drush updatedb after installing and enabling each module

Hi, I'm attempting to install Drupal 8 manually, according to the instructions on the official Drupal documentation, page: https://www.drupal.org/docs/user_guide/en/install-manual.html. I am attempting to do so on a remote server, which I am using to host my website. I would like my main website, www.xyz123.com, to be separate from my Drupal site, which I want to access using subdomain.xyz123.com.

Hello,

I recently tried to upgrade to drupal version from 8.6 to 8.9 via composer. It seems all packages upgraded successfully but i unable to access frontend and can see following error