And finally, today the domain of sillybutterfly.nl has been transferred and the associated e-mail accounts have been activated on the VPS. This action had complications because the publisher's webshop still runs on Drupal 7. This was necessary because we work with Ubercart, and the payment modules that link Ubercart to our payment provider Mollie do not work under Drupal 8. The main reason for our migration is that we want to build a webshop in Drupal 8 (and in the future Drupal 9 etc.), but you really can't do that without Composer.
So I also had to install Drupal 7 and make it accessible, in a way that is very similar to how I do it with Drupal 8, so with symbolic links.
It all worked and it works! So we are now completely over... with the exception of the now functionless sbgs.nl and without the migration of vuurplaats.eu. I have already done a test migration of this, but I will only proceed after consultation with the customer. There is no rush because the subscription at Robohost.nl runs until November.

So... we have arrived! Thanks to Plesk. In retrospect, I think that's a nice program. Let's see if I can't install something like this on my home server as well, that makes management a lot easier.