Drupal 8.x

This is just a general notice that there may be some difficulties with Bluehost regarding SSL certificates.  I have three sites running there as subdirectories under one account.  All three lost use of a certificate (that had been good for some years now).  Some error reports say the certificate expired - other messages say otherwise.  Anyway, I purchased a new certificate yesterday - to no avail.  I don't know if this is an issue with Drupal or Bluehost in general.  Bluehost is now known as a Wordpress platform.  Their tech support tells me they are looking into it.

I inherited a Drupal site. When I attempt to switch php I receive the following error.

Fatal error: Declaration of Drupal\Core\Database\Statement::fetchAll($mode = null, $column_index = null, $constructor_arguments = null) must be compatible with PDOStatement::fetchAll(int $mode = PDO::FETCH_DEFAULT, mixed ...$args) in /core/lib/Drupal/Core/Database/Statement.php on line 169

Do I need to update Core before I can update php?

Thank you.

I'm trying to upgrade a simple Drupal 8.9.20 site to Drupal 9 so I can get to 10.  I followed these instructions but when I run composer update I get this.

Would love to download a version of the Group Domain module compatible with Drupal 8, but can't find it..where do I go?

I first banally launched a composer update that miserably failed with some incompatibility.

Problem 1
    - drupal-composer/drupal-scaffold[2.5.0, ..., 2.6.1] require composer-plugin-api ^1.0.0 -> found composer-plugin-api[2.2.0] but it does not match the constraint.
    - Root composer.json requires drupal-composer/drupal-scaffold ^2.5 -> satisfiable by drupal-composer/drupal-scaffold[2.5.0, ..., 2.6.1].

Then I tried to follow the documentation at the URLs below.

Hi- Hoping someone can help!

I'm trying to upgrade a Drupal 8.8.1 site, eventually to D9, but initially to 8.8.4 (which I read somewhere is a needed waypoint for some module). After backing up and manually moving the new core+ files in place, it crashes with the error "'CommerceGuys\Addressing\AddressInterface' not found". Addressing is a library required for the Address module, which is required for Commerce, etc.

According to the Address module info, manual installation isn't possible, so I tried using Composer to reinstall/upgrade Address, but I'm getting this error: