Howard Miller

Firstly, almost none of this is a Moodle issue. Exept that, if the hostname/URL of your Moodle site has changed as a result of what you've done, you will need to change the $CFG->wwwroot setting in Moodle's config.php.

Anyway, when you say you "set a new DNS for my domain" can you explain exactly what has changed / what you did?

I would guess that you have chaned the hostname and the Apache configuration doesn't have a VirtualHost directive for the new name. So it doesn't know what to do and you are getting the default (Apache) page.

Depends... how did you install MariaDB on your server in the first place?

^^

What he said. /usr/bin/php is some incompatible (unknown) version of PHP. /usr/bin/php80 is, presumably, PHP 8. It works. Move on....

Are you trying to use an Oracle database?

I'm not aware of one.

If you have the facility you would need to write something but (see above) it's probably not a good idea.