We have LetsEncrypt and Zero SSL on DirectAdmin, but all of them have limits on sub-domain installation. I was wondering if we could install Wildcard SSL and use it as shared SSL for all Sub-Domain accounts created under the Domain name.
Really, you need more than 100 sub-domains? That's a lot.
But yes in that case a wildcard certificate is required, because that is only 1 entry and if you use seperate entry's then there is a limit of 100 in total.
So just use a wildcard certificate for your domain name like *.domain.com and then you should be fine because that is only 1 entry and it's valid for sub1.domain.com
sub2.domain.com
and so on.