Answer to #6: I think I messed up the branch on previous merge request and it seemed to be rather cumbersome to fix. I tried to merge the 6.3.x to the branch that was based on 6.2.x so it had all the changes shown as they are coming in on my merge request as a new files and chagnes. Closed that and created new branch based on 6.3.x and added code there as it was before. Still haven't made tests, but they are coming in the near future and then I will open the request again.
konstara → created an issue.
https://www.drupal.org/files/issues/2024-02-26/3415445-cant-load-non-eng... →
For meantime as the core gets updated with solution that eventually closes this, here is a small workaround patch for this particular problem.
konstara → made their first commit to this issue’s fork.
https://www.drupal.org/files/issues/2024-02-26/3415478-cant-load-non-eng... →
Created this for workaround where no collation changes are required.
Workaround where no collation changes are required.