Upgrading Drupal

After the update, Composer complains:

 Problem 1
    - Root composer.json requires npm-asset/chart.js ^4.4 -> satisfiable by npm-asset/chart.js[4.4.0, ..., 4.5.1].
    - npm-asset/chart.js[4.4.0, ..., 4.5.1] require npm-asset/kurkle--color >=0.3.0,<0.4.0 -> found npm-asset/kurkle--color[0.3.4] in the lock file but not in remote repositories, make sure you avoid updating this package to keep the one from the lock file.

But in the lock file I have

Drupal\Core\Extension\ModuleHandler->invoke() (line 352 of core/lib/Drupal/Core/Extension/ModuleHandler.php).

Has anyone had a similar problem? Something is duplicated somewhere, but where?

Problem/Motivation

After upgrading my site from Drupal 10 to versions 10.6.0 and 10.6.1, pasting text into CKEditor 5 (in "Full HTML" format) stopped working. A critical JavaScript error appears in the browser console:

ckeditor5-dll.js?v=47.3.0:5 Uncaught TypeError: Cannot read properties of undefined (reading 'fromPosition')
at R. (media-embed.js:5:29557)

Steps to reproduce

The problem appears precisely when trying to paste text (paste action).

After updating from Drupal 11.2.10 to 11.3.0, I see a white screen with the following error: (try again later)
The following error appears in the log.

TypeError: Drupal\Core\Utility\ThemeRegistry::getGlobalPreprocess(): Return value must be of type array, null returned in Drupal\Core\Utility\ThemeRegistry->getGlobalPreprocess() (line 193 of /var/www/vhosts/sparrowhouse.nl/httpdocs/core/lib/Drupal/Core/Utility/ThemeRegistry.php).

I have a multi-site set-up with 4 sites running. 1 Out of the 4 is not working after updating core to 10.6.0. The following error is shown when I access any admin page:

An authoritative site shows (validator.w3.org)
Trailing slash on void elements has no effect and interacts badly with unquoted attribute values.
<meta name="viewport" content="width=device-width, initial-scale=1.0" />

How to remove slash?
<meta name="viewport" content="width=device-width, initial-scale=1.0"> This is good