Is it possible to create and use wildcard SSL certificates in Plesk?
How to configure Plesk to automatically assign a domain wildcard certificate for new subdomains?
Plesk allows to create and use certificates for wildcard domain names (like *.example.com). Wildcard certificate can be created the same way as usual certificate is generated. The only difference is that the name with “*” sign is specified in the left path. For example, “*.example.com”, will match all subdomains, like mail.example.com, ftp.example.com, etc.
When a subdomain is created within the same subscription, then there is no need to manually add wildcard certificate to the subdomain. The wildcard certificate of main domain is automatically assigned to the newly created subdomain.
Instructions to get a free wildcard certificate are available here.
To create Let’s encrypt wildcard certificates, see instructions here.