Hello everyone!
I write here about the community, to prevent anyone from making the same mistake as me.
I had the bad idea of changing PHP from 8.0 to 8.1, at first it seemed that everything was fine, except for a few WP plugins that were giving problems, the rest worked fine.
After a few days I activated a new domain with "site newdomain.xx -wp" when starting the installation procedure on the browser ... the bitter discovery, the newly created site responded with an error 500!
In short, fortunately with the downgrade to 8.0 the previously created site was able to complete its configuration.
for 12 hours I was in a panic ... I just couldn't understand.
Moral of the story? don't rush too far, you just risk falling!