@DieterWerner
If you have access to DNS, you could simply point DNS A records to the IP of your V-Server and use the Let's Encrypt extension.
Just do the following
1 - select a domain that you own and set DNS to point to the IP of your V-Server via an A record, (and)
2 - change the hostname of your V-Server via Plesk Panel to <domain>.<tld>, as chosen in step 1, (and)
3 - do a reboot from the command line, just to make sure, (and)
4 - run the command
dig <domain>.<tld> +short, just to verify that your A record and associated IP settings (see step 1) are propagated across the internet, (and)
5 - go to "Tools & Settings > TLS/SSL Certificates > Let's Encrypt (click)" and fill in the right domain (the <domain>.<tld> from step 1) and press OK,
and that should work......... and if it does not, just respond in this thread.
By the way, it is
highly recommended to rename the hostname of your V-Server (as opposed to using *.stratoserver.net) AND create an individual A record to point to the IP of the V-Server, since that will also relieve the problems associated with bad reputation that might occur or often occurs with the use of the default domain *.stratoserver.net.
Regards......