Post installation

problem:
valid json responses get tagged by resourceresponsevalidator as non valid

description:
I am a bit of a loss debugging an suddenly emerging error on my local dev environment (MAMP, php 7.4, D8 and D9) where totally valid json responses get tagged as non valid.
The json is partly generated bij Drupal and parts come from an external unrelated source.
Reports gives me reasons like

Dear All, somehow I managed to create a field on the entity type user but it does not show under ../admin/config/people/accounts/fields. From ..admin/reports/fields I see the field but the field does not have a value in the "Used in" column! How do I remove the field so I can create the field correctly? Regards Thomas S

Drupal version 10.x, drush 11.6.0 and I am trying to connect to a remote server that is accessible only by IP address. I have not been able to get the alias file to work so in order to simplify debugging I am trying (site name and ip address obviously redacted below):

drush --root=/var/www/html/mysite --uri=http://aaa.bbb.ccc.ddd status

The above does not work. Partial output when adding -vvv shows:

I can send mail in general in Drupal 10.1.2, but when a user tries to make an account, the mail is not sent.

I get: Error sending email: An email must have a "To", "Cc", or "Bcc" header.

Where do I fix this? The user does have an email in the people listing.

I found two Hard sites that use drupal and both use the same theme (you recognize it at first sight) could someone expert tell me which theme it is? It would help me a lot and I would appreciate it. using chrome in dev option I can't find the theme.. I doubt it's a custom theme because it's used on two different sites and it's the same..

[two spam domains redacted]

Hi, after upgrading to Drupal 10 the PHP filter module does not work. I'd like to be able to put some php code in a block. On the Drupal Module site you can read the following: "There are better alternatives out there".
Where are those alternatives?