Check your email - you should have received my message via the now working contact form on https://salaroche.com/Contact.php!
Once you've confirmed receipt, I'll go in and remove the old files that are no longer needed.
I had to add the mysqli folder, make a new email body file (webassist/email/contact.php) and removed one of the server validations which was linked to a hidden field and seemed to be causing issues.
I didn't need to add any of the mail parameters your web host suggested - it worked with the default settings.
It would also now be a good idea to ask your web hosts to upgrade the PHP version again. The new contact form and related files should work just fine on PHP8, and there's nothing else I can see on the site that uses PHP.